#am literally gonna post this and run bc i'm embarrassed lmaoooo you'd think i'd have gotten used to posting about weird dicks but i have NOT

[makoodlesarchive]

darling it’s better (down where it’s wetter)

i finally finished it omg lol, genuinely thought this would never be done

thank you so much to everyone for being patient with me and sending me all those cute little asks talking about the fic, that actually really helped with writing it!

For the love of all that is holy, please check out this absolutely incredible art of merbakugou by @crowolina​!

pairing: bakugou katsuki x reader

word count: 14k

warnings: mentions of drowning, explicit sex, interspecies (?) sex, that merman dick yo

 masterlist | tip jar

The humidity outside is so high that the air is sitting thick and stagnant -- it feels like it could be cut with a knife. It’s uncomfortably hot, and the air feels almost damp and sticks wetly in your throat as you breathe. Sweat pools in all the most uncomfortable crevices, until the desire to get into the water is less of a passing fancy, and more of an all-consuming need. You slip carefully down the hill, over the dry grass, until you hop down into the fine sand that makes up the little beach in the sheltered cove at the bottom of the hill.

The cove is protected by natural cliffs on either side, with the only access point being the hill that your uncle’s house sits on. It’s small, but the stretch of sand is soft and golden and clean, absent of any tourists and the debris that they tend to leave behind. It is, by all accounts, perfect, and a far better option than the significantly more crowded beach fifteen minutes away. Thanks to the hill and the natural caves, the air is cooler and easier to breathe in the cove. You set out your towel and water bottle near the base of the hill and strip down to your bathing suit, hefting your inflatable floaty up and preparing yourself to march into the ocean. After all the time spent inside your uncle’s grody house, the fresh air and fine golden sand feels like heaven.

When you finally work up the nerve to dip your toes into the water, you have to fight not to recoil from the cold. The temperature of the water is cool and chill, a direct contrast to the heavy, hot thickness of the air, and it takes a few minutes of psyching yourself up before you’re able to submerge yourself fully. Despite the chill, the sensation of being surrounded by water is a relief after the oppressive afternoon heat. You wade out further, keeping a mindful eye out for the reefs your uncle had mentioned, until the water comes up to your hips, then your chest, then your collarbones. You let the tension seep out of your shoulders as you float, buoyed gently by the waves. It’s the most peaceful you’ve been since your stay with your uncle began after he broke his leg; you don’t mind taking care of him while he heals, but you didn’t quite realise how much you needed a break until now.

The saltwater is like a balm; it takes some manoeuvring to actually get yourself up on the floaty, but once you’re settled and relaxed you think you could happily float on your back like this for hours, lost to the warmth of the sun on your skin and the waves rocking you back and forth. The fresh smell of the saltwater and the soft swaying of the floaty in the ocean waves lull you into a peaceful doze. 

Naturally, that’s when things start to go wrong.

As you fall into a light sleep you fail to notice the thick grey clouds rolling in and the tide pulling out. The waves creep higher and crash faster, and your floaty bobs rapidly along as you sleep, unaware of just about all of it. 

That changes when the floaty catches on a sharp rock jutting out of the water; awareness comes crashing back to you as the floaty tears right as a wave breaks over you, the acute chill of the water and the weight of the ocean pushing down over your head. The shock of the cold water leaves you momentarily stunned and in the brief moment before you start thrashing against the icy waves, a riptide catches your legs and tears you through the water.

Panic rears up in your chest, sharp and choking. Your chest is already aching from the lack of air since you hadn’t had the chance to get a proper breath before you had gone under, and you’re not able to thrash against the current with as much force as you need to be able to reach the surface again. You kick frantically against the water, muscles burning, but you’re so disoriented that you’re honestly not even sure if you’re swimming in the right direction; the salt burns your eyes when you try to open them, and everything is so dark that you can’t tell which way is up.

Your head crests the surface of the water, and you just manage to suck in a painful breath when another wave crashes down over the top of your head. As you struggle to right yourself and reach the surface again, you find your movements becoming sluggish. You’re panicking and running out of air, but even though you know that you still can’t manage to fight your way to the surface.

For a moment something pale cuts through the water in front of your eyes and you think that you’re about to emerge into the air again but you feel so impossibly tired. Your vision begins to go dark, and your limbs are so heavy that continuing to struggle against the tide is impossible. 

You know that you’re sinking, but there’s not a thing you can do to stop it.

Consciousness returns to you slowly and painfully. 

The first thing to register is the soreness in your chest and ribs -- every inhale is an effort, and it feels as though your lungs are actually bruised. You inhale sharply, which causes a chain reaction of hacking and sputtering and retching. The coughing, in turn, highlights how just about every part of your body feels as though it’s been battered continuously against a rock. When you finally crack open your eyes, you wonder for a moment if you might have gone blind, because your vision stays exactly as dark as when your eyes were closed. When you push yourself up into a seated position, however, you find that you’re sprawled on the wet, rocky floor of a cave. 

You move your head very slowly to take in your surroundings, feeling woozy and nauseous. You wonder if you hit your head, or if the nausea is a side effect of nearly drowning. Panic begins building again in your chest, and you have to make a concentrated effort to push all of your uncle’s warnings about delayed drowning out of your mind so you can focus on taking deep, even breaths.

The rocky floor that you’ve woken up on is a ledge of solid stone that makes up half of the cave; the other half is submerged in a pool of clear seawater, beyond which a large crack in the stone walls leads directly back to the ocean. The entire cavern is dimly illuminated by what seems to be phosphorescent algae growing in the water and along the dampest patches of the walls, glowing a muted, luminous blue. It's pretty, but you can’t concentrate on it because in the dim light provided by both the entrance to the cave and the algae, you can see the bottom of the water is littered with what looks like bones.

You look away quickly, because that is not conducive to staying calm. The bones are probably from some stupid large fish that got stuck in the cave and couldn’t figure out how to escape, and you are absolutely not going to look any closer to confirm that. A flash of colour catches your eye, though, and when you turn to look you find the deflated, torn plastic remains of your floaty hanging from an outcrop of rock. 

Amidst the enormous relief at being alive, there’s a growing sense of unease in the back of your mind -- how had you washed up inside the cave in the first place? The entrance to the cavern is nothing but a slash in the rocks, angled in such a way that it would be nearly hidden if not for the thin slant of light shining through. How had you not been dashed to bits by those viciously sharp rocks like your floaty? Even if you had miraculously been washed through the small gap and into the mouth of the cave, by all rights you should have ended up floating in the saltwater pool. How had you ended up on the ledge?

You cast another slow look around the cavern; if you weren’t so sore and scared, you think you’d be able to appreciate your surroundings a lot more. The cave is actually quite beautiful -- the algae in the water gives the pool an almost other-wordly, luminescent blue hue, and the stone ledge is devoid of slimy seaweed or sharp barnacles which makes for a somewhat comfortable place to sit, despite its dampness. The deep booming of thunder from outside the cave is what forces you to realise that you’re not going to be able to get out of here until the storm dies down, but at the very least you could have been stuck somewhere far worse. Other than the bones sitting at the bottom of the pool, the cavern is oddly clean.

It’s only when you realise that your whole body is trembling that you take the time to check yourself out. The cold has caused your circulation to slow, and your hands and feet are painfully stiff and bloodless. While the cave isn’t as chilly as you might expect, it’s still not exactly warm and you have no idea how you’re supposed to stop your shivering. You know that you’ve read survival advice regarding hypothermia before, but now that it’s actually necessary it seems as though all relevant knowledge has leaked out of your brain. 

Your eyes rove the cavern absentmindedly as you think, wracked with the occasional violent shiver. “Fuck,” you whisper to yourself, exhausted. Your gaze passes smoothly over the outcrop of rocks near the cave’s entrance, the red eyes staring up at you from under the water, the froth churned up by the waves spilling through the entrance and into the cave. Another clap of thunder booms from outside.

It takes a ridiculous amount of time for your brain to catch up to what your eyes had just seen, but when you finally jerk your attention back to the water, whatever you had seen is gone. Your breathing is laboured now and stings in your chest slightly, but you pay it no mind as you shuffle closer to the edge of the pool, staring intently at the now empty spot in the water. Maybe your near-drowning experience had resulted in more oxygen deprivation than you had realised, because you could swear you had just seen a man in the water.

“Hello?” you call. Your teeth are chattering, the tone of your voice both nervous and hopeful in equal measures. The cave echoes your voice back to you in a way that makes you feel distinctly idiotic. “Is s-someone there? Please!”

The surface of the water ripples, but you’re pretty sure that the movement is due to the waves rather than some mysterious man hiding in the pool. Feeling disappointed and a little dumb, you sit back and gaze morosely into the water. Were you really so addled that you were beginning to hallucinate?

Before you can begin to worry too much about your possibly declining mental state, the water ripples again. This time, you snap your head up in time to see something dart behind a large rock sticking up from the water. 

“Hey!” you blurt, sitting up and scooting closer to the edge. “Who are you? I c-can see you, asshole!” 

It occurs to you that it’s highly likely that you’re sitting here shouting at a scared seal or something else much less menacing, or human-like, for that matter. You only have a short moment to feel extremely stupid before whatever is out there moves again, and when a head pops out from behind the rock you fall totally silent.

It is a man! His shock of blond hair is wet and plastered to his head and most of his body remains hidden behind the rock, but there’s no denying that it’s an actual person and you can’t help the immediate relief that washes over you.

“Hey, d-did you get washed up in here too?” As soon as you ask the question, you realise that something isn’t quite… right. How had you missed him on your first glance around? It wasn’t as though there were all that many places within the cavern to hide, and there shouldn’t be any reason to hide in the first place; you had been unconscious, after all. Why was he still in the water?

And why wasn’t he answering you? His head is tilted slightly and his gaze is boring into you, but he makes no move to speak or to come out from behind the rock. It hits you then that you’re all alone in an isolated cave with a total stranger who’s positively glaring at you, and you’re wearing nothing but your bathing suit.

Cold unease settles deep in your belly, and you push yourself carefully away from the edge. His eyes follow the movement; you can’t be sure from this far away, but his irises look an almost unnatural shade of red. The hair on the back of your neck and all up your arms stands on end, and you can’t shake off the feeling that you’re in danger.

“I was just leaving,” you tell him, forcing a nervous smile to your face. “I’m just trying to figure out how to get out of here.”

The man doesn’t reply; in fact, he barely even reacts. He doesn’t even blink.

The smile slides slowly off your face, and your throat makes a dry clicking noise as you try to swallow. “Okay!” you say too loudly; your voice echoes throughout the cave, which only frays your nerves further. “I’m going!” Even as you say it, you realise that there’s no possible way out of the cavern without having to get in the water and swim past the man to get to the crack in the cave wall. Water spills through the crevice as waves crash into the side of the cliff, and another clap of muffled thunder reminds you that there is a storm raging outside. Even if you manage to get around this weirdo and escape the cave, you don’t know how far you’ve drifted from the cove. With the ocean so unsettled, it would be plain stupid to dive back out there without knowing where you are or how deep the water is outside of the cave.

The sound of water rippling catches your attention, and you look back at the man to see that he’s beginning to emerge from behind the rock. Your spine stiffens, alarmed at the sudden movement after so much uninterrupted stillness. He keeps low to the water, his face half-submerged, and as he slides out from the rock and begins to smoothly cut through the water. A flash of colour catches your eye and draws your gaze towards the side of his head. Right over the space where his ears should be is delicate soft orange and black webbing that almost looks like…  fins? They twitch a little in your direction, but otherwise hang limply so that they’re almost hidden by his mass of spiky hair.

The fins are distracting enough that it takes you a truly embarrassing length of time to notice that the man has an even stranger feature that his odd ears. As he gets closer, you finally catch sight of the long, lithe tail.

Your instinct is to draw back in both shock and disbelief, but as soon as you move the man (was this even a man?) lifts his head fully out of the water and bares his teeth at you as he spits out a low, sharp hissing sound. You freeze, overwhelmed; your eyes are darting from his teeth to his fins to the tail, but you’re having some serious trouble actually taking it all in. The oxygen deprivation from nearly drowning must have done more damage than you had first thought if you’re beginning to hallucinate shit like this. The tail is long and serpentine, ending in twin webbed fins and covered in dark scales. Combined with his disturbingly human torso, he must be nearly eight feet long. When he reaches the edge of the rocky platform, one of his hands comes up to grip onto the surface and you’re greeted with the sight of long and dark clawed fingertips. They flash in the low light like a threat, ensuring you keep as still and quiet as possible. From this close, you wonder how you possibly missed the fact that he is most definitely not human. 

Your breathing picks up as you struggle not to panic, and the fins on the sides of his head rotate towards you as the air sticks harshly in your throat. It’s undoubtedly a threat display; the way the fins splay out flat makes him look aggressive and frightening, and you want to cringe away but you’re also afraid to move. You just tense up on the spot and try to make yourself smaller, hoping desperately that he’ll lose interest once he realises that you don’t pose any danger to him.

“I’m just trying to get home.” Your voice comes out croaky and shaking with fear. You seriously doubt that he can understand what you’re saying, but the sound of your voice has his head tilting suspiciously at you. Even if he doesn’t understand your words, maybe your low and pleading tone will assure him that you mean no harm. “I don’t know where I am, I’m cold, and I’m sore, and I just want to go home.”

A translucent second pair of eyelids slide sideways in a blink, and you have to fight to suppress your shiver. From this close, he’s so obviously inhuman that it’s downright unnerving. His skin is smooth and blemishless, almost too perfect. His features, while human, are virtually flawless in a way that’s actually quite overwhelming -- he’s beautiful, once you ignore his fish half. And the blood-red, glaring eyes.

Predictably, he remains silent, though the fins on the side of his head drop low. You really hope that’s a good sign, and decide to keep talking. Hopefully, by familiarising him with your voice you lower the chance of him attacking you. “My uncle is probably so worried about me. He broke his leg a month ago in a boating accident, and I’ve been looking after him since. This is the first time I’ve taken any time to myself -- I don’t even know how long I’ve been gone for. He must know something’s wrong, or else I would have come home as soon as the storm hit.”

The creature just blinks that sideways blink, floating still in the water as he stares at you.

You sigh, and ease back slowly into a more comfortable sitting position. Those orange fins rotate towards you at the movement, but otherwise he doesn’t react. You take the lack of hissing as a sign of progress. 

“This is your cave, huh?” You keep your tone stupidly conversational, as if you’re having a friendly chat with a neighbour or something. “It’s nice. Pretty cosy, as far as caves go. Clean. Except for, you know. The bones.” Now that you’ve mentioned it, you can’t help your gaze from drifting to said bones. To your relief, you see that most of them seem to be the remains of various ocean creatures, though there are a few suspiciously large bones that are almost certainly human. Fear rises up through your chest and lodges in your throat, which makes it difficult to force your words out. “Wow. Yeah. The, uh. The bones are kind of gross.”

The creature follows your gaze, craning his head over his shoulder to see what you’re looking at. He pushes himself away from the ledge and dives in one quick, fluid movement, startling you so badly that you nearly overbalance despite sitting down. His tail is pure muscle, and it ripples as he cuts through the water. It’s only now as you watch him submerged beneath the surface that you realise this is a real mermaid creature that you have somehow found yourself trapped in a cave with. The realisation sends you reeling, but before you can spiral into a flat out panic attack, the creature bursts out of the water again. He pulls himself up onto the ledge and leans on it with his forearms, before slapping down an object right in front of you.

It is, quite unmistakably, a human thigh bone. You recoil in badly disguised horror, “Oh! What the fuck!”

The creature watches you, unblinking. He seems… expectant?

You look down to the thigh bone, then back to the creature. Is he threatening you? Is this his way of letting you know that he’s killed humans before, and is willing to do so again? You cringe away from the yellowing bone. 

“Oh shit. Fuck. Oh my god. Okay. Okay, um… I’m not a threat! I promise! I don’t even want to be here. Please don’t hurt me. Shit, you don’t even know what I’m saying, do you?” Your voice has grown thick with panic, and you try to choke it down. Your hands are trembling, and you run them nervously over your face in an attempt to do something with them. “Look. You, uh. You seem like a very nice… mermaid? Mer… creature. I can tell that you’re, um, very strong. And your claws are very intimidating.” You trail off, because you’ve ended up freaking yourself out and losing your train of thought.

The creature has lifted itself a little further out of the water, and appears to be puffing up slightly. You wonder if it’s another threat display, but he doesn’t seem to be overly aggressive. That is, until a clawed hand reaches out and snatches at your ankle so fast that you can barely follow the movement with your eyes. You yelp with fright a solid moment too late, but the pain that you had been expecting doesn’t come. Instead, those sharp, mottled black claws grip firmly at your ankle without actually piercing the skin; the creature appears to be peering closely at your feet.

“Those are my toes.” You tell him stupidly, as though he has any idea what you’re talking about. “They don’t taste good.” You wiggle your toes, and the creature jerks back and hisses at them. “Whoa! Sorry! They’re harmless, I swear! Please don’t kill me!”

When it becomes clear that your toes don’t present any immediate threat, he pinches your big toe between two fingers and squeezes it experimentally. The fear that had been so paralysing is beginning to steadily fade the longer this little exchange goes on without the creature hurting you. You could almost fool yourself into thinking that maybe he was harmless, but the bone sitting on the ground next to your hips suggests otherwise. Still, aside from his initial display of aggression, he doesn’t appear to be particularly hostile. Just a little… over-curious.

His grip on your legs is strong but gentle enough to not actually be causing you any pain, though that might also be thanks to the fact that your extremities have gone numb from the cold. Your shivering has eased up a bit, but you still feel exposed in your damp bathing suit. You’re a little self-conscious, but you’re pretty sure that the mermaid man is too preoccupied with your feet to even notice the fact that you’re in a state of undress; in fact, you’re not even sure if he has a concept of nudity, considering he’s half fish.

You’re so preoccupied with watching the creature rub at your shins that it takes a while for you to notice how quiet it’s gotten inside the cave. “Sounds like the storm has blown over.” You tell the creature, who just stares at you with his brow furrowed. You’re not entirely sure where to go from here; you have no choice but to start searching for a way out of the cave, but you’re not sure how to go about extracting yourself from the creature’s grasp. You don’t know if he’ll stay as docile with you once you’re actually standing and moving around. “How am I gonna get out of here, huh?” 

The grip on your leg disappears as the creature backs up before plunging back into the water with a quick snap of its tail. You can’t help but marvel at the sheer power hidden in that muscular lower half as he powers through water almost faster than your eye can follow. He disappears from view, and it takes you a few seconds before you realise that he’s darted down a passage that you hadn’t been able to see due to the angle. 

As soon as you realise he’s gone, your stomach clenches. “Hey!” You call, suddenly nervous. It might be stupid, but at least when he was here you weren’t entirely alone. “Hey, wait! Please don’t leave me here!”

There’s no sound but the gentle tinkling of water against rock. You sit back with a gusty sigh and shut your eyes. While he wasn’t the most chatty of companions, there was something slightly reassuring about the fact that you weren’t entirely alone in this cavern. Maybe him leaving was for the best though; if he was the one responsible for the mass amounts of bone littering the bottom of the pool floor, then it would be safer for you now that he’s gone. It looks like you’re going to have to get back into the water and swim to the entrance, and while you fill with dread at the thought of having to return to the cold water, it’s probably significantly safer to do so now that the creature is nowhere to be seen.

You slip off the edge of the ledge and into the saltwater pool, hissing as the cold water hits your skin. It’s deeper than you had initially thought; your feet aren’t even close to touching the bottom. You clutch at the ledge and breathe, even though the deep breaths feel like they’re slicing into your lungs. Your feet feel oddly heavy, as though they’ve been carved from blocks of ice, and you feel doubt stab at you; are you going to be able to swim like this?

The water ripples, signalling movement behind you, and you realise that the creature has returned. You have a split second to panic -- if he decides to attack, you’ve just put yourself right in his path -- but then you catch sight of what he’s pulling behind him. It looks like a surfboard that’s been broken in half.

“Oh, wow!” You gasp, reaching out for it. It’s faded and corroded by time, disuse, and saltwater, and there are several deep gouge marks on it that look like suspiciously like claw and teeth marks, but it’s buoyant and definitely more than enough for you to paddle out on. “Amazing! Oh, you’re such a good boy! Thank you!”

Talking to him like he’s a dog probably isn’t the best idea, but his fins rotate towards you and even though he bares his teeth, he doesn’t look entirely displeased by your tone. He also doesn’t move to try and eat you, though his exceptionally sharp teeth are still pointed in your direction. You hope very much that it’s just posturing and that you’re not misinterpreting his body language; the last thing you need is to get torn apart right when you’re trying to make a break for the exit. He lets you take the surfboard and watches as you attempt to drag yourself up on it. It’s easier said than done, considering it’s been broken jaggedly in half and you can’t touch the ground. You might even be embarrassed by how much you’re struggling if there was anyone else around to see it; as it is, you feel like even the creature is judging your flailing legs as he bobs in one place effortlessly.

Apparently, he gets sick of watching your ineptitude very quickly. “Woah!” You yelp as a sharp, scaly hand lands on the curve of your ass. “What the fuck!” The hand pushes at you, shoving you up on the surfboard from behind. You don’t even have the presence of mind to be surprised at his strength, because you’re too focused on the hand on your ass. “Woah, woah, okay, buddy, no groping please!”

The creature’s tail lashes in the water as he stares blankly at you. His hand doesn’t move.

You try to squirm away, but there’s nowhere to go and he is technically helping. “Fucking hell.” You groan. It’s not as if he understands that he’s groping you; he’s a fish. “Okay. Okay, fine. I will overlook this so long as you help me get out of here.” 

The creature shows no sign that he understands your attempts at bargaining. In fact, as soon as you speak he releases his tight grip on your ass and begins to loop slow, lazy circles around you. You sit up, straddling the broken surfboard as you watch him circle you. Now that you’re next to him, you realise that he really is huge -- his tail is long and practically ripples with powerful muscle, and his human half sports well-defined abdominals and bulging biceps, too. His lazy movements and the way that his gaze never once strays from you, not even to blink, sets your hair standing on end. This creature is a predator, and you’d be naive to let your guard down for even a second.

You swallow, and pray that he can’t smell your fear. When you begin to paddle your way towards the cave entrance, the creature perks up and begins to follow. He keeps up with the circles even as you paddle, and you can’t help but scowl at him. “That’s kind of obnoxious, you know.” you tell him, and receive another toothy grimace. If it weren’t for the way his lips peeled back off his sharp teeth, it might have looked almost like a grin.

Watching him in the water is surreal. He moves through it so fluidly that it’s almost mesmerising, and you have to redirect your attention back to paddling several times after getting distracted. Apparently your progress is too slow for him, because the next time he circles around, he reaches out and curls his claws into the board. Wood splinters under his grip, but he doesn’t seem to notice as he yanksat the board insistently. You sit back as the board is pulled through the water, happy to let him do all the work. 

Maneuvering the makeshift raftthrough the narrow entrance takes some effort, but you mostly allow the creature to work you and the board through the gap. And with that, you’re out of the cavern and into the open ocean. The sky is a dull, purple-tinged grey, the sun having already sunk low beyond the horizon; it’s evening time, which means you must have been in the cave for hours. You twist on the damaged surfboard and crane your head around to look back at the cavern; the entrance is barely noticeable, merely a crack in the face of a towering cliff. 

Your heart jumps as you realise that you recognise this cliff. Your eyes follow the length of it, and sure enough you can see the cove in the distance and the shape of your uncle’s house sitting on the hill. “Ah!” you exclaim in delight, a relieved smile breaking over your face. Home! You’re so close! When you glance down at the creature, you see that he’s followed your gaze. He looks back to you, and his tail lashes the water. You point towards the cove. “There. That’s where I need to go. My home is over there.” You only feel a little stupid for talking to him like he can understand; he might not comprehend your language, but he’s obviously intelligent and he’s brought you this far. It’s not too far-fetched to hope that he might bring you just a little bit further.

Your optimism pays off -- the creature dutifully begins pulling the board in the direction you had pointed. In the twilight, you can see that the scales on his tail are an iridescent black colour, flashing deep orange as light reflects off him as he twists and turns in the water. It’s pretty, and you watch in silent admiration. When he begins pulling you faster and splashing through the waves with unnecessarily large flourishes of his tail, you realise that he’s showing off.

You laugh, delighted with the display and giddy now that most of the danger seems to be behind you. “Yes, yes, very impressive. Your tail is beautiful.” 

Obviously pleased with your admiring tone of voice, the creature preens and flexes as he cuts through the waves. With his speed, what should have been a fifteen minute swim is cut down to barely five, and he releases his grip on the board as you begin to approach the shore. As soon as the water is shallow enough for you to stand, you slip off the board and curl your toes into the sand. You turn to grin at the creature, elated, and see that he’s retreated into the waves so that all you can see of him is his eyes and the top of his head.

“Thank you!” You call, grinning as you stagger out of the sea and back onto dry land. “You’re amazing!”

In a flash of scales, he disappears into the waves. You stand on the beach for several long moments, watching the place he had been and wondering if you had just experienced some kind of extremely advanced auditory and visual hallucination. You stay until you start to shiver again in the cold evening air, then stumble your way back up the hill to your uncle’s house.

Predictably, your uncle is a healthy mixture of angry and terrified. It seems you really worried him, and he had no way to contact anyone since he doesn’t own a cellphone. Despite your exhaustion, it takes the rest of the evening to calm him down and assure him that you’re fine. Eventually, you get to slip away for a warm bath and then to bed. 

Lying in bed staring at the ceiling of your uncle’s guest bedroom, you’re sure that it will take you ages to get to sleep. Your brain replays the events of the day over and over again, until the details become murky and your thoughts slow. The last thing you think before you slip off into sleep is how lucky you are to be alive, whether you were hallucinating or not.

You’re an idiot. A total, complete imbecile.

That’s the only explanation for how you’ve managed to find yourself back at the jagged mouth of the cave yet again. It’s been almost a full two weeks since you washed up here during the storm, and in those two weeks you could swear that you had seen a blond head bobbing in the waves in front of your uncle’s house multiple times. It was pretty hard to convince yourself that the whole mermaid-slash-sea creature thing was a product of your imagination after a scary and traumatic event when the hallucination kept appearing right outside where you live.

So, you had borrowed an old surfboard from your uncle (a full, undamaged one this time), and paddled your way back out to the cliff face. You notice almost immediately that the tide is strong here, and it’s difficult to keep yourself from being dashed right against the jagged surface of the cliff. It does confirm your suspicions, though - there’s no way that you could have washed up inside that cave by chance. It takes a significant amount of effort to pull yourself inside the mouth of the rocky structurecave without being crushed into the sharp stone slabs decorating the outside like some sort of deadly decorrocks, but you manage to do so without hurting yourself. 

Inside, the cave looks exactly the same as last time, though this time it’s empty. You paddle forward, the movement significantly easier now that you have a full-sized surfboard. Peering around, you see no sign at all that anything living might have occupied the cavern. That’s when the doubt starts to come creeping in. You’d had the odd invasive thought over the past two weeks that maybe you had imagined the whole mermaid creature (because it was, admittedly, insane), but then you had seen that blond head floating in the ocean breeze on several occasions. You could have sworn he was watching the house! Now that you’re here and facing the complete absence of evidence, you start to feel a little silly.

You paddle further into the cave, straddling the board so that your legs can kick out through the water. You admire the phosphorescent algae growing up the walls, amazed at the natural glowing light. When you turn your attention back to the bottom of the pool, though, you go still. 

It’s empty. The floor of the pool, previously littered with bones, is totally pristine.

You sit still on the surfboard in the middle of the pool, gazing down into the water. Despite how crazy the whole situation was, you had been sure that you weren’t imagining it. But now, faced with the complete absence of evidence, you’re forced to consider the fact that maybe the whole thing really had been in your head. You have such a vivid memory of the silt-covered bones blanketing the floor of the cave that now seeing them missing has completely thrown you off.

A bark sounds behind you, rough and deep like a seal, and you jerk hard in surprise.

Whirling around, clutching at the board beneath you to keep your balance, you catch sight of the creature floating by the entrance to the cave. He’s watching you intently, having obviously been monitoring you since you first managed to float inside.

The relief that slams into you feels like a physical punch -- the spikey hair, red eyes, and tail are exactly the same as you remember. It’s real. You laugh, and it feels like the sound has been ripped right out of your chest; the situation is almost overwhelmingly surreal, but the endorphin rush of knowing that you’re not delusional has you grinning at the creature, wide and bright.

“Hi!” You say, trying to keep your voice as level as possible despite your elation. You may have been delighted to see him, but you have no idea if he even remembers you from two weeks ago; you can only hope that he doesn’t decide that he’s hungry today. “Wow, look at you! You have no idea how good it is to see your face! And your tail! God, I am so glad to see your tail! It’s real, holy shit.”

One of the creature’s webbed fins twitch on the side of his head, rotating towards you as you ramble. In a single, smooth movement he pushes away from the entrance of the cave until he’s right in front of your surfboard, his face half-submerged in the water. He seems pretty docile today, his movements strong, but relaxed. The aggression he had displayed that had scared you so badly the first time is completely absent, and he begins to loop circles around you in a manner that is almost playful. You don’t bother to hide the awe in your expression as you watch his serpentine lower half undulate through the clear water. 

“Wow.” You breathe, your cheeks stretched wide by your goofy grin. “It’s amazing.”

He must feel your gaze on him, because his lazy looping begins to become more elaborate. The extra flourishes he makes with his tail as he circles you splashes water all over your thighs and stomach. You squeak in surprise, but as you relax again you start to laugh.

“Are you showing off?” You ask with a grin, watching his body roll through the saltwater pool, never straying too far from your surfboard. “You’re just a giant puppy, aren’t you?”

His circling gets faster and faster, until watching him nearly makes you dizzy. It’s a little reminiscent of being stalked by a shark, but you don’t sense any aggression or animosity from him at all. The little hairs standing on end on the back of your neck serve as a reminder that he is, undoubtedly, a predator, but you don’t feel as though he poses any particular threat to you right now. It’s a dangerous game you’re playing, treating him like a harmless puppy dog, but you have a feeling that his bark is probably worse than his bite. At least, you hope so.

“Help me get to the ledge?” You ask, beginning to paddle over. He catches on to where you’re trying to get to almost instantly, and pushes the surfboard effortlessly over to the rocky platform. 

Once you climb out of the water and turn to him, he pushes his upper half up onto the ledge and leans on his folded arms. The intensity of his gaze has lessened, or maybe you’ve just gotten used to it, because it doesn’t feel as though he’s trying to eat you alive with his eyes anymore. His tail swishes through the water, creating gentle waves rippling over the surface as he watches you with a sort of attentive stillness reminiscent of a cat.

“You saved me last time, didn’t you? When I was drowning?” You ask absent-mindedly. Your voice subconsciously takes on the same artificially high-pitched tone you use when you’re talking to animals and babies, but judging by the way his fins rotate downward and flatten to the side of his head he doesn’t like that. “Thank you.”

You’re taking a massive chance even making an attempt to touch him, but you take a deep breath and then hold your breath as you reach out to him. He flinches from your outstretched hand and bares his sharp teeth at you, but there’s no animosity behind it and he makes no move to stop you from placing your hand on the top of his head. His hair is coarse with sea salt, which probably explains its spiky texture, and is still dripping wet. As you ruffle his hair, your fingers curl into the chaotic blond spikes -- though you had originally intended to simply give him a pat on the head, you end up playing with his hair and scratching at his scalp.

You weren’t sure how the creature was going to react to your bold decision to give him head scratches, but he seems to like it -- his eyes go half-lidded and droopy, and he presses his head lightly into your touch. You grin, encouraged by his reaction, and let your hand trail cautiously down to one of his fins. It’s soft to the touch and delicate, with an almost silky smooth slippery texture. It twitches beneath your fingers, and you notice for the first time that the soft orange colour is interspersed with milky streaks of black. 

“Pretty.” you murmur to him, stroking a finger down the length of the fin before returning your hand to his messy mop of hair.

A harsh, rumbling growling sound erupts out of the creature’s chest, and you whip your hand back in shock. The creature’s head jerks up to look at you, equally startled by your sudden movement. It takes you a moment to realise that he wasn’t snarling at you, he was purring.

“Oh!” you breathe, surprised. “You like me playing with your hair?”

The creature obviously doesn’t answer; instead, he reaches out and grabs your wrist, his sharp claws cautiously guiding your hand up to plant right back into his hair. You laugh, startled by his sudden boldness, but obediently start scratching at his scalp again. That snarling, chain-saw like purr starts up again, and you can’t help the breathless giggle that bubbles out of you at the sound of it. 

The minutes tick by as you play with his hair, his grumbling purr echoing throughout the cave. His body has gone mostly lax, with his upper half laid out on the ledge in front of you and his lower half floating in the water. It’s kind of exciting being so close to a creature that could probably kill you with a single swipe of his claws but has instead chosen to let you pet him. Like this, lying relaxed by your legs, you could mistake him for a regular man. So long as you didn’t allow your gaze to drift lower, at least.

Your stomach decides to end the moment by letting out a rumbling growl of its own, which surprises even you since you had eaten before you left your uncle’s house. The creature draws back, squinting suspiciously at your torso.

“Sorry,” you say sheepishly, embarrassed despite yourself, “I’m not actually hungry, my stomach doesn’t know what it’s talking about.”

The creature blinks one of its creepy sideways blinks at you, and then in one quick movement disappears under the water with a flourish of his tail. You catch a streak of colour darting out of the cave and sigh as the water settles, disappointed that the moment has been brought to such an abrupt end by something as stupid as your tummy rumbling when you weren’t even particularly hungry. You settle back and wonder if you should take that as a sign that it’s time to get out of there.

The cave is beautifully peaceful, silent but for the sound of the waves lapping against rock. You could probably stay there for hours, but it doesn’t feel right to be there without the creature; it feels as though you’re infringing on his private territory, somehow, and it makes you feel a little uneasy. In the end, you don’t get much time to overthink -- the creature re-enters the cave nearly soundlessly, and you barely notice his presence until he emerges out of the water and hauls himself up on the rocky platform next to you.

“Oh!” You blurt, startled by the sudden movement. “You’re back!”

The creature doesn’t react to your words at all, instead dropping something in front of your folded legs. You blink at it, bewildered, as it wriggles on the stone platform.

“It’s… a fish.” You point out redundantly, at a loss for anything else to say. When you look back up you find that the creature is watching you carefully, a hint of impatience on his face. He nudges the fish towards you, and you cringe back as the fish flip-flops helplessly. “Gah!”

The creature’s brow drops into a frown, clearly unhappy with your reaction. He pushes the fish towards you more aggressively this time, but when the fish leaps into the air it’s only instinct for you to smack it away in a panic. The fish bounces once and then makes a bid for freedom, jumping straight into the water. The creature snarls and leaps after it.

The poor fish doesn’t stand a chance; the creature snatches it back up within seconds, and then it’s dumped in front of you again. “Uh. I don’t really… want this?” You stare at it, and then lift your head to look at the creature. He’s still frowning, and when you make no move to take the fish he reaches out to pick it up himself with a grunt of obvious irritation. You relax a little once he takes the fish, wondering what the hell that had been about.

Smack.

You screech as the fish slaps into your face, recoiling so violently that you overbalance and fall flat on your back. “What the FUCK!”

The creature rears back, obviously surprised by your reaction and all the yelling. He spits out a hissing sound as the fish makes another escape attempt, and dives after it. You’re too busy scrubbing at your face in disgust to keep track of what the hell he’s doing now, but when something wet and slimy smacks into your arms you realise that he’s just pelted you with the fish again!

“Why would you do that!” You yell, distressed. You would never be able to forget what a fish to the face feels like, now. “Fucking- That’s fucking gross!”

A low grumbling starts in the creature’s chest, but his brow is furrowed and his head is tilted so he doesn’t seem angry. If anything, he just seems confused. The fish is still wriggling where it’s stuck in his clenched, clawed fist, but its movements are getting progressively weaker. 

“Don’t you dare throw that at me again,” you threaten, glaring his way and injecting as much authority into your voice as you can manage, “Or we will have a serious problem.”

Your tone must have been pretty clear, because the creature doesn’t try to launch the fish at your face again. Instead, he lifts the fish up to his own mouth and takes an enormous bite, ripping the head right off and chewing it between his razor-sharp fangs.

You gag at the sight of guts and viscera falling to the cavern floor, and then turn to retch as wet chewing sounds reach you. “Oh fuck, that is nasty. Why? Ah, Jesus-” The creature proffers the chewed up fish carcass, scowling when you turn your face away to gag again. “Stop shoving that at me! I will get sick on you!”

The creature grunts, confused and annoyed by your behaviour. When it becomes clear that you will not be taking the remains of the fish to eat yourself, he tosses the carcass to the side. It lands with a sad little ‘thwunk’ and then lays forgotten as the creature turns back to look at you. Your stomach rolls as he starts to pick raw meat out of his teeth with a clawed fingertip.

“On that note, I think it’s time for me to leave.” You climb to your feet, stubbornly refusing to look at the dead fish. “That’s enough weirdness for me to deal with for one day.” As soon as you make a move for the surfboard, the creature starts making sharp barking noises at you. You turn to scowl at him, irritated, and see that he’s dragged himself after you along the ledge. “What do you want?”

The creature looks almost constipated for a long moment, before he huffs a sharp breath of air out his nose. “Stay.”

It feels like the world stops turning. You think your heart might have actually stopped in your chest. You were surely hallucinating this time. “Did you just speak?”

The creature’s tail lashes impatiently as he scowls up at you from the ground, obviously displeased at your sudden difference in height. “Will you fucking sit down?”

You drop back down to the floor, jaw hanging open. “What the fuck?” You whisper to yourself. It feels as though your brain is functioning several steps behind its usual pace, and all you can do is stare dumbly. “You can fucking talk?”

“Are you an idiot?” The creature snaps at you, scowling. A dusting of light pink blooms high on his cheekbones, “I’m talking right now, aren’t I?”

“I’ve been talking to you this whole time!” You yell, horrified. You cast your mind back desperately, struggling to recall whether you said anything embarrassing at any stage. You definitely have, you just know it. “What the fuck! Why did you never answer?!”

The creature clicks his tongue, and an infuriating little smirk settles over his perfect features. His voice is smug when he speaks next, “I’m a good listener.”

That does it. 

“Oh, fuck you.” You jump to your feet again and march to your surfboard, ignoring the scrabbling sounds against the rock as the creature pulls himself after you.

“Hey! Wait! You said you’d stay, asshole!”

“No, you told me to stay! I never agreed to shit!” You snap, embarrassed and annoyed. You fumble with the board, and the creature takes that moment to shove it away from you. You gasp in outrage as you watch it float out into the middle of the pool, then round on him. “What the hell!”

The creature glares at you, his cheeks stained red. It looks as though he’s seriously struggling with something, until he finally says, “Stay… please.” It sounds as though the word has been forced out of him, like it actually grates him to say it.

You should probably leave. But then again, how many chances in a lifetime are you going to get to meet a fantasy creature (and one that can actually speak to you!). Your curiosity gets the better of you (and the embarrassed but hopeful look on the creature’s face doesn’t help), so you reluctantly sit back down once more. You don’t miss the way he seems to relax a little now that you’re not going anywhere. “Only for a while.” you warn him half-heartedly.

The creature scoffs as if he doesn’t care, as if he didn’t literally just plead with you to stay. “Whatever. Why didn’t you like the fish?”

“The-?” You glance over your shoulder. The fish carcass lies abandoned several paces away, stinking and leaking everywhere. “Uh…”

“I thought you were hungry.” he presses, sounding distinctly as though he’s accusing you of lying.

“You were trying to feed me?” You ask, raising your eyebrows so high they nearly vanish into your hairline. That’s what smacking you in the face with the fish was all about?

The creature’s tail twitches again, sending waves rolling across the surface of the pool. He looks embarrassed, though he’s making a pretty valiant effort at pretending to be unaffected. “Yeah, so what? It’s not my fault that your fingers are all blunt and useless. Can you even kill anything with those?”

You squint down at your fingers, then frown at him. “I don’t know, I’ve never tried! Humans don’t eat raw meat, anyway!”

“Yes, they do!” The creature shoots back, “I’ve heard of sushi!”

That effectively renders you silent as you blink at him. Where had he heard of sushi? “Okay, fine!” You concede grumpily, “Some people eat sushi! That is not the same as catching a fish and eating it live!”

The creature makes a face and lies out on his back, stretching leisurely. “Damn, you’re high maintenance.” He complains, though he doesn’t look all that annoyed. If anything, he looks stupidly pleased with himself. “Whatever. Tell me what you like, then.”

“I don’t know,” You shrug, chewing your lip, “Normal food, I guess. Like, from the store.”

The creature frowns at that, obviously displeased but thinking hard. After a moment he grunts, shrugging. “We’ll work something out.” He says vaguely, then moves on before you can respond. “You’re staying with Aizawa now, right?”

You blink in surprise. “You know my Uncle Shouta?”

“Your uncle?” He asks, avoiding your question.

“Well,” you amend with a shrug, “We’re not blood-related. He’s always been a close family friend. How do you know him?”

The creature shrugs, muscled chest rippling in a way that’s frustratingly distracting. “He’s always hanging around in his stupid little boat.” There’s an underlying current to his voice that sounds like begrudging respect. “He’s helped us out a few times, I guess. He’s alright.”

“‘Us’?” You repeat, eyes wide. “Are there more of… you?” You gesture at his tail, unsure of what to actually refer to him as.

The creature must decide that he’s said too much, because he changes the subject. “What am I supposed to call you, anyway? I can’t keep thinking of you as ‘dumbass’.”

You scoff, slightly offended at that, but tell him your name anyway. “What do I call you?”

“My name is Katsuki,” he grins at you, displaying his rows of very white and very sharp teeth. “But you can call me whatever you like.”

The low, easy rumble of his voice sounds almost flirtatious, and for a long moment all you can do is blink at him. There’s no way you’re reading the situation correctly, you’re sure of it. “Um. Katsuki is fine.”

Katsuki snorts, but doesn’t push the matter. Instead, he rolls onto his side so that he can watch you more closely. His gaze is searingly intense, so much so that you genuinely have difficulty meeting his stare. His attention is overwhelming, and so you find yourself looking around the cavern in an effort to distract yourself. Your surroundings are more or less unchanged from the last time you were here, with one exception -- though the cave was clean before, now it seems to be immaculate. The absence of the bones littering the floor of the pool makes the water seem deeper and clearer, light reflecting off the surface and dancing in ripples along the rocky ceiling. Any seaweed or lichen that had been growing around the rocks or up the walls is gone now, leaving the stone surfaces looking as though they’d been scrubbed clean.

For lack of anything better to say to fill the silence, you say, “Your, uh, cave looks great. Very… tidy.”

Katsuki appears to puff up at that, proud that you noticed. “Yeah? You like it?”

“Oh, yeah. Definitely.” You nod absently. “It’s… um, cozy.”

“Cozy?” Katsuki repeats. He’s edging closer, almost imperceptibly, but the dragging sound his scaly lower half makes on the ground gives him away. His gaze has sharpened, and you feel distinctly hunted.

“Uh,” You laugh, nerves pitching your voice several octaves higher than normal. “Yeah, I guess. That’s some very nice, uh, algae. It really… pulls the room together.”

The algae, in all its phosphorescent glory, is nice, but Katsuki doesn’t turn to look where you’re pointing. The tip of his tail drags in the water, where it thumps softly from side to side. “Want to see the rest of the place?”

Something about his tone of voice has you hesitating; it sounds pointed, as though his words are heavy with significance that you don’t understand. Still, you don’t want to be rude, so you smile nervously and say, “There’s more? Sure, I’d like to see.”

Katsuki inhales sharply through his nose as an anticipatory grin spreads slowly across his face. His features, handsome anyway, are intimidatingly good looking as his cheeks dimple with his smile, and you only have a moment to wonder what exactly you’ve just agreed to before he pushes himself back into the water in one smooth movement. “Come on.” He says, reaching a hand back up to you and waiting impatiently for you to take it. 

You pause for a moment, before throwing any lingering sense of self-preservation to the wind and taking his outstretched hand. He’s mindful of his claws as he helps you into the water, but it’s impossible to miss the way his palms drag over your arms in a way that can’t be mistaken for casual. 

It’s only when you’re floating in the water next to him that you’re able to fully comprehend the sheer size of him. While his torso is mostly human in both shape and proportion, he’s still built like a damn bodybuilder, with solid abs and rolling biceps. Even without the tail he’s pretty big, but with it? You guess it must be about eight feet long, and it curls around you in the water like a thick, dark snake. He smiles at you as he keeps you afloat, and his teeth glint in the low light. It’s border-line terrifying, and for a long moment you wonder if you’ve just made a very serious mistake.

But then his tail undulates and he’s cutting through the water, dragging you with him. You laugh, startled, and cling onto his neck as he swims through the pool and down the mostly concealed passage he had disappeared through the last time.

The passage is completely submerged in water, and narrows before widening into an even larger cavern area. You gasp quietly as you realise that this is definitely his living space.The layout is pretty similar to the previous cavern, with a shelf of rock jutting out of the wall of the cave just above the height of the water, but unlike the previous cavern this rocky shelf is covered in soft dry moss. You wonder if this is where he sleeps.

The luminescent algae is far more plentiful in this part of the cave; it grows all up the walls and along the ceiling, where it glows in the dark like stars. You crane your head all the way back so that you can gaze open-mouthed at it all, awed by the surreal beauty of it. “Wow,” you breathe in delight, “It’s stunning!”

Katsuki grunts out a pleased rumble in response. In the position you’re in, you can feel it vibrate in his chest. When he reaches the platform, he grips you by the hips and boosts you up onto the rock. The sheer strength takes you by surprise, especially considering the way in which his expression hardly changes as he lifts you with ease.

Once you’re comfortably seated on the moss-covered stone, Katsuki heaves himself up to join you. His tail slaps against the water and coils close to your legs, rubbing gently against the skin of your legs. The sensation of wet scales should feel a little gross or uncomfortable against you, but they feel silky soft as they brush your skin. You lay back against the moss, gazing up at the glowing blue algae painted across the ceiling.

“Your home is beautiful.” You murmur, keeping your voice low. It feels as though the moment is fragile, and you don’t want to break the peaceful atmosphere in this little grotto.

Beside you, Katsuki gives a smug little shrug of his shoulders. He’s sitting way too close to you to be entirely casual (his tail is practically draped over you at this stage), but he doesn’t seem to think anything of the closeness so you write it off as a mermaid thing. “Obviously. What, are you fuckin’ surprised?”

You ignore that, sighing happily as you get comfortable. You can feel Katsuki’s gaze settle like a weight over you, but you simply refuse to look over -- lying comfortably on the cushioned cave floor and gazing up at the fantastical luminescence of the walls and ceiling is a kind of peace that you’ve never experienced before. You feel like you could stay like this forever.

However, Katsuki does not like to be ignored. Your attention has only been directed away from him for a few moments before he starts shifting irritably beside you. You can feel the muscles in his tail moving as it rolls, his clawed fingers tapping impatiently against his abdomen. It seems as though he’s waiting for something in particular, but you have absolutely no idea what this could be. 

After another few moments of impatient shuffling, you finally turn your head to frown at him. “Is something wrong?”

Katsuki frowns back at you, and you see a brief hint of uncertainty flash in his eyes before it’s snuffed out. “No. I’m being fucking patient.”

“Patient?” You parrot, confused. “What are you waiting for?”

For the first time, you notice the flush crawling up the back of his neck and spreading over his cheeks. Swearing quietly, he looks off to the side and shuffles a little on the spot. Eventually he speaks again, though he still doesn’t meet your eye. “Am I reading this wrong?”

“Uh-?”

He continues before you can properly answer, his jaw clenched tight. “I tried to show you that I’m a good hunter and a strong opponent, but you didn’t like any of the bones. I wasn’t sure if you were interested or whatever, but then you showed me where you lived.” The emphasis he places on his words makes you realise that there is some special sort of significance that has gone right over your head, “Then you came back to my cave again, so I figured we were on the same page. But then you refused the fish-”

“I-” you start, bewildered, but Katsuki just keeps going as he works himself up into a mini rant.

“-Even though I know you’re hungry! And you said you liked the changes I made to the place after I got rid of the bones, and you kept calling my tail amazing and beautiful and shit-” He ignores the way you choke a little at that, though he seems to run out of steam, “I just-- fucking, tell me if I’m reading this wrong. I don’t know shit about humans. I thought you were accepting my advances.”

Advances? You inhale so sharply that you nearly choke all over again. There’s no way he means what you think he means. There is no damn way. “Are you- are you coming onto me?”

Katsuki stares back at you, before his face crumples into a scowl. “Hah? Are you fucking dumb? I brought you to my living space and gave you bones! I tried to feed you fish! Of fucking course I’m coming onto you!” His voice drops then and takes on an uncertain edge to it, “I thought you were accepting my mating advances.”

Your jaw drops, and you honestly can’t find the strength to close your mouth. Mating advances? “I-” you start, then cut yourself off. It feels like the world has tilted just slightly off to the side, throwing you off-kilter. You have absolutely no idea what to say. “Give me a minute.” You blurt, darting to your feet and turning away from him to pace. 

You quickly encounter a problem, in that there’s nowhere to pace to; the ledge is only so large, so all you can really do is march from the edge to the wall. Overall, it’s only about ten paces long, and the whole time you’re focusing on not slipping on the moss. It doesn’t exactly give you a lot of space to think, but your mind still goes into working overtime.

You sneak a peek at Katsuki -- he’s lounging exactly where you left him, but his eyes are sharp and alert as they follow your movements. Not for the first time, you take notice of how unnaturally handsome he is; his features are perfectly formed, his skin clear and flawless where it stretches and swells over his finely muscled form. He looks like a handsome prince from a storybook, and you hate that you’re feeling sparks of attraction towards someone who’s half fish.

Katsuki clearly notices you looking at him, because he stretches out to display his body in a way that’s distinctly suggestive. You look away quickly, embarrassed at having been caught staring. How would that even work?

You can’t believe you’re even entertaining the idea.

“I’m not gonna fuck a fish.” You breathe, eyes clamped shut. “I’m better than that.”

“Who the fuck are you callin’ a fish?” Katsuki snaps. His tone is heated, but the way the split fins at the end of his tail slap a steady rhythm against the ground reveals his excitement. He must have caught on to the fact that you’re actually considering it, because the fins on the side of his head have begun to wiggle a little in anticipation. “Will you stop overthinking it and come over here?”

You hold onto your pride and dignity for another few seconds before abandoning them altogether and padding back over to him. You fold yourself down into a sitting position in front of him so that you’re facing each other. Katsuki sits up quickly, his lips beginning to turn up in a grin. You ignore the anticipation flashing over his face, and ask, “So, how does this, um, work?”

Katsuki inhales sharply, obviously excited. His fins flap softly against the side of his head. “Let me show you.”

“Right, okay. Yeah.” You say stupidly, eyes widening as Katsuki leans in. Any further rambling is cut short as he presses his lips into yours.

The kiss is a little clumsy at first -- Katsuki is careful with his sharp teeth, but the feeling of them pressing against your mouth sends a little frisson of excited fear down your spine. It’s only when he’s pressed up against you like this that you realise there’s a stark difference in your body temperatures; Katsuki’s skin is cool and soft, which feels amazing pressed against your rapidly heating body.

He pulls away from the kiss, leaving you blinking stupidly after him, and then pushes at your shoulders to guide you down onto your back. The moss underneath you acts like a cushion, so it’s significantly more comfortable than you had been expecting. This ends up being a good thing as Katsuki lowers himself down on you, his weight pinning you to the floor.

“You’re so warm.” He murmurs, nuzzling into your throat before nipping softly at it and snickering when you jerk at the sting. His hands skim over your sides, his clawed fingers dragging harmlessly over your vulnerable skin.

You hate to admit it, but there’s something about the danger of the whole thing that’s really getting you going. You recall the bones that had previously cluttered the whole cave floor, and know that Katsuki not only could rip someone apart if he felt like it, but had done so before.  You squirm beneath him, pressing your thighs together as he kisses at the sensitive junction between your throat and ear.

Apparently unhappy with the position, Katsuki leans back a little so he can pry your legs apart. As soon as you drop your knees open he squirms into the gap and presses himself right along the line of your body, dropping aggressively eager kisses all up your chest and throat. “Take this off.” He rumbles, tugging irritably at the strings to your bikini top.

“Um.” You say, thoughts a little hazy. Every time Katsuki moves the muscles in his tail shift and roll, and his tail is pressed right in between your legs. “Off. Right.”

Katsuki watches as you tug the fabric off, his eyes bright and impatient. No sooner have you tossed your bikini top to the side than he’s on you again, thumbs rolling over your nipples as he pushes his face into your breasts. “What the fuck,” he mutters, squeezing curiously at one breast and licking a stripe over your other one, “You’re so soft.”

 Desperate to touch back, you reach up and run your hands through his salt-coarse hair. When you accidentally brush against one of his head fins, his reaction takes you by surprise – his whole body jolts, pressing into you harshly, and he groans a little into your ear. You do it again, grinning as Katsuki’s hands abandon your tits so he can grab you by the hips.

Maybe your own excitement causes you to forget yourself, but you can’t help but grind your hips up into Katsuki where he’s pressed in between your legs. Katsuki laughs a breathless, snarling laugh before grinding back into you, the base of his tail just under where his human half ends pressed flush against your covered pussy. Katsuki, still gripping you by the hips, grinds repeatedly against you – the scales on his tail create an almost ribbed texture, and every time they drag over the front of your bikini bottoms you can’t help but twitch your hips back against them.

It doesn’t escape your notice that you’re virtually dry-humping a merman on the floor of a cave, but you simply push that aside for now; you can feel yourself getting wet, and you know that most of your critical reasoning skill go out the window when you’re horny.

You’re so distracted by the nipping, stinging kisses and the way Katsuki’s tail grinds and wiggles against you that it takes a very long moment to realise that the feeling of his tail pressing against you has… changed, somehow. You pull back, breathing a little heavy, and look down to try and see what’s different, but Katsuki is pressed so closely to you that you can’t see past his chest. You don’t get a chance to look properly, either, because then Katsuki begins to slide down your body until his head is between your legs.

He tugs at your bikini bottoms, but his inexperience with legs becomes clear as he tries and fails to successfully remove them. “Fucking- take these off!”

You snort at his impatience, but obediently wiggle your way out of them. It’s actually a relief to be out of the wet swimwear, but you don’t have much time to appreciate it before Katsuki’s face is in between your legs and pressed right up to your now exposed pussy. He inhales deeply as you squirm, mortified. “Don’t- stop fucking sniffing me there, oh my god!”

“Hah?” he squints up at you, “Why?”

“It’s embarrassing!”

Katsuki frowns, clearly not understanding what the big deal was. “You smell good.”

You’re pretty sure that you don’t, considering virtually nobody’s genitals smell good (especially not after being trapped in a damp swimsuit for hours), but his tone is so matter-of-fact that you can’t bring yourself to argue. He doesn’t wait for a response anyway, burying his face between your thighs again and huffing as he inhales your scent. You cover your face out of sheer embarrassment, but don’t make any effort to pull away.

When his tongue starts to prod at your clit, your whole body jerks in surprise. His tongue is cool, a stark contrast to the heat pooling in your folds, and it feels startlingly good as it squirms against you. Your hips twitch and chase after his touch, but he keeps you firmly in place with his grip on your hipbones.

“Humans are pretty different down here,” Katsuki says conversationally, his words vibrating against your pussy lips. “I’ve never seen anything like this.”

“Oh yeah?” you say absently. Your thighs flex around his head from the effort of not clamping down hard around his skull.

He hums, then licks at your slit unashamedly. He grins, apparently pleased with the taste. “I’ll get used to it.”

“Can you- there’s, um, a spot. Higher up. Could you-?”

Katsuki doesn’t take direction particularly well, and it takes a couple of moments for him to actually locate your clit. When he does find it though, he licks and sucks at it so eagerly that your back actually bows right off the ground.

“Shit!” You gasp, wriggling against Katsuki’s face. “Oh!”

Encouraged by your noises, Katsuki just doubles his efforts. The wet, slurping noises are obscene, and your moans echo around the cavern in a way that sounds distinctly eerie; you’re so thankful that there’s no one else around for miles to hear.

“You’re so warm,” Katsuki murmurs, sounding slightly breathless, “Are you this hot on the inside, too?”

“Oh god.” You whimper, head swimming. Without even really knowing what you’re asking for, you whisper, “Please.”

Katsuki perks up at that, then drags himself back up so that his face is level with yours once more. This close, you can see how shiny his face is after being buried against your wet pussy for so long. When he kisses you, you can taste yourself on his tongue. It makes you whimper again, pressing into him eagerly. Katsuki is breathing pretty hard too, and when he presses his torso against you, he groans long and low.

This time, with the base of his tail pressed against the bare flesh of your cunt, you know for sure what you’re feeling; there’s an honest to god bump that definitely wasn’t there before, right where you might expect a dick on a human male. Katsuki notices where your attention is straying to, and brings one of his own hands down to massage the bump. It’s only then, as you peer closer to get a better look at what he’s doing, that you see what looks like a vertical slit positioned a few inches down from where his human half ends and his tail begins. His clawed fingers dance around it, rubbing at the swollen flesh around it without touching the slit itself.

Your curiosity gets the better of you, and you reach out your hand to stroke at the same place Katsuki is. The pads of your fingers run over the textured scales, earning a soft grunt as he presses eagerly into your touch. You repeat the same massaging motions Katsuki was doing, and as you watch, the slit seems to open wider.

It happens slowly, then all at once. As you rub at the sides of the opening, the tip of what appears to be Katsuki’s penis begins to slowly distend. You nearly pull back from surprise, but then Katsuki lets out a quiet, soft little moan, and you can’t bring yourself to pull away from him. You run the tip of your index finger around the inside of the slit, and find that it’s soft and almost rubbery, reminiscent of what you imagine sealskin must feel like. At your touch, his penis extends the rest of the way.

 You blink, then sit back. “Oh.” You say stupidly, gazing at his dick.

Katsuki straightens up and sits back smugly, clearly proud of what he was packing. He seems to miss your growing alarm entirely. “Like what you see?”

You purse your lips and take a moment to collect your thoughts. “It… moves.” You say faintly.

Katsuki doesn’t look very impressed with your analysis of his penis. “Yeah. Obviously. C’mere.” 

His dick is significantly pinker than his own skin tone, thick at the base and then narrowing along the length. It’s big, uncreased and smooth, and when you wrap your palm around it (ignoring Katsuki’s desperate thrust into your fist) you find that it has the same almost rubbery texture as the skin around the slit. It’s just a few shades warmer than the rest of his body, though still significantly cooler than a human; it’s odd, holding a dick that feels almost cool to the touch.

Katsuki’s tail lashes agitatedly at the ground behind him, though he doesn’t do much more than press a little harder into your hand. “Done looking?” he grinds out, clearly beginning to run out of patience.

“No.” You say absently, giving his dick a few pumps and watching him hunch over with a choked moan. His dick is practically prehensile, and wriggles in your hand like it has a mind of its own.

It’s completely unnerving and alien and really, really weird, and you hate yourself because all you can do is wonder how it would feel inside of you.

“Y/N,” Katsuki grunts, his tail slapping agitatedly against the floor behind him, “Can I? Please, can I?” The please sounds as though it’s been pulled unwillingly from him, though it seems no less genuine because of that, and he leans down to nip impatiently at your shoulder.

“Yeah.” You breathe, relinquishing your hold on his dick and watching it slap against his abdomen. You lie back onto the moss, breath hitching as Katsuki eagerly drags himself up the length of you.

 The sensation of his thick heavily muscled tail nestling in between your legs and shifting with every one of Katsuki’s little movements has your head swimming, and your knees fall open even wider. His head drops to your chest and his mouth latches onto one of your nipples, humming as your head falls back with a pleased sigh. You can feel the hardness of his cock on the inside of your thigh, can feel the tip of it moving just slightly, tracing the sensitive flesh close to the crease of your hip.

When Katsuki looks up to meet your eyes, you’re not prepared for the level of franticness in his gaze. He looks needy, his proud features twisted in desperation even as his eyes burn. “I’m going to mate you now.”

“Okay.” You say dumbly, clutching weakly at the moss beneath you.

The tip of Katsuki’s dick is unexpectedly soft as it presses into you, and far slicker than you had expected. You peer down at his hips, and notice for the first time that the slit that his penis is protruding from is leaking some sort of membranous fluid. You wonder if maybe you should feel grossed out by that, considering the foreign fluid is being pressed inside of you, but all your brainpower is being diverted to the slow, wet slide of his dick stretching you open.

Katsuki moans, long and low, as he clutches at your hips. “Fuck!” he hisses, baring his rows of sharp teeth. He’s obviously trying very hard to hold himself back and enter you slowly, but he’s practically trembling from the effort.

“Okay, okay, okay.” You chant, breathing heavily. Katsuki’s dick is big, and the pressure of the stretch is just bordering on painful despite the slick slide. You wonder if you’re going to feel the ache of this for days or weeks.

And then he’s all the way in, the rough, textured scales of his tail pressed flush against the backs of your thighs. Both of you have to take a moment, panting. The pain of the stretch begins to fade, and you begin to feel like you’re just on the right side of full.

You want to feel Katsuki move, and so you wrap your thighs around his hips. The scales scratch a little at the delicate skin on the inside of your thighs, but it’s so worth it for the way Katsuki groans, and the way the fins on the side of his head flap minutely. One of his palm’s plants itself firmly in the moss by your head, the other clasped tightly over your hip.

The muscles in his tail ripple and his dark scales flash in the low light as he pulls his hips back only to slide back in, smooth and fast. It’s hard to catch your breath, because the slickness of his cock sliding in and out of you is at once foreign and desperately arousing. Katsuki seems to feel the same way, because his mouth is dropped open and his brow scrunched, eyes half-lidded as he humps into the slippery heat of your pussy.

“You’re so hot,” he groans out with a huff as his hips stutter, “Feels like you’re burnin’ me.”

Dazedly, you sympathise with him; his body is several degrees lower than your own body temperature, and the coolness of his dick inside of you has every one of your nerves hyper-aware and attuned to it. It feels beautifully refreshing against your own heated flesh, the contrast almost overwhelming.

Katsuki pets absently at your hip and thigh as his thrusts begin to come faster and harder; he builds up a steady rhythm, one that seems to seek as deep inside of you as possible and quickly renders you speechless. The only sound filling the cave is the wet slapping sounds from where Katsuki is pounding into you and the grunts and pants and moans that each of you make without shame.

You feel each thrust and slippery slide inside of you so acutely, as if every one of your nerve-endings is straining towards him. The texture of his cock inside you feels so alien, and you could swear you feel it actually aiming for the spot inside of you that makes your limbs turn to jelly. You wonder if your own body feels as strangely foreign to him; you’re guessing it does, judging by the way he pants and humps into you with that wild look in his eyes. Or maybe that’s just how he usually is during sex. It’s not like you have any sort of frame of reference for sex with mermaids.

You reach down to rub at yourself, jolting a little as your warm fingertips come into contact with your heated clit – you’ve become adjusted to the cooler body temperature of Katsuki,  and now your own warmth almost feels like too much. You wonder how the heat of your cunt isn’t completely overwhelming for him, but considering the dark flush overtaking his face and chest and shoulders, and the way that his jaw hangs open and his eyes have gone glassy, you think maybe it is.

He hikes your thighs further up on his waist without pausing his thrusting, the scales scraping oddly along your bare calves. “I’m gonna-” he grunts, pushing his face into your necks as his tail slaps harshly against the ground every time he fucks into you, as if he’s lost control over it.

You rub harder and faster at your clit, gasping as Katsuki bites down on the tender skin of your throat. It’s not hard enough to break the skin, and seems more like he’s trying to keep you in one place, but the threat of his sharp teeth against such a vulnerable part of you sends you hurtling towards the edge.

It only takes a few more strokes, and another twist of his cock against your g-spot, before you come hard and silently, open-mouthed and wide-eyed.

“Fuck, yes.” Katsuki groans throatily into your neck, his movements only becoming increasingly intense. It feels as though he’s trying to plow you right through the rock (which is actually an incredible turn-on, though you don’t want to admit it) and you whimper and gasp as you begin to pass into the realm of oversensitivity.

Katsuki’s upper body goes taut as his powerful tail pushes him forward into you one last time, so deep that you swear you feel the tip of his dick moving against your cervix, and then he comes with an honest to god snarl. You sigh as you feel the slick gush of his cum inside of you, thicker than you’d expected, and flop bonelessly once you know he’s done.

“Holy shit,” You breathe, staring wide-eyed at the cave ceiling. The glowing algae twinkles back at you as Katsuki breathes slowly and deeply into your neck, his thick arms winding around your waist and shoulders. As the haze of your orgasm begins to fade and reality starts to set in again, you’re struck with the fact that you’ve just fucked a mythical creature, and his very weird fish dick is still inside of you. “Oh my god.”

Katsuki grunts, clearly not pleased that you’re ruining his afterglow with delayed panic. “Shhh, s’fine.” He mumbles, rubbing at the bitemark on your neck in what he apparently thinks is a reassuring manner, “You’re mine – ain’t nobody gonna hurt you.”

The two of you are clearly on different wavelengths, but you don’t bother to think to much about that particular statement. “I just fucked a fish.” You breathe. It sounds just as ridiculous out loud as it did in your head.

“You liked it, too.” Katsuki says smugly, not denying the fish part this time around.

“Dickhead! Get off me!” You say irritably, embarrassment beginning to sink in.

“No.” Katsuki mumbles childishly, snuggling into your neck and holding you tight so you can’t struggle. His dick shifts inside of you, and he grunts as you automatically clench down around it. “Stay.”

The moss is comfortable, the cave is pretty, and Katsuki’s arms around you feel better than you’d like to admit. You relax, the weight of him laying on you more soothing than you had expected, and close your eyes. “My uncle is gonna kill me.” You say, an afterthought flitting through your mind. He was so worried the last time you disappeared into the sea like that, you can only imagine what he’s going to say once you come home late after doing it again.

Katsuki snorts and kisses the base of your throat, and you feel like you could probably lie in this cave forever, listening to the sound of the ocean ebbing and flowing just outside the rocky walls. “If he’s gonna kill you,” he murmurs, lips dragging over your skin, “I’d hate to see what he’d do to me.”