#bsd theories

[thedreamofadaydreamer]

A BSD theory that I have for a long time is the idea of reincarnation, the idea that all ability users have multiple lives.

Fyodor seems to know too much about ability, particularly about Beast Beneath the Moonlight , Francis may know about the connection with the Book, Shibusawa may know it is one of the two anti-abilities along with No Longer Human, but to know exactly its status as the Bookmark? When Atsushi is only 18 and awake this ability in 12? Not to mention Fyodor is also the one telling Shibusawa of his skill, so he must know beforehand about Byakko, maybe even before Atsushi was born.

He also possesses a good chunk of information about Mirror Lion, two ability weapons Amenogozen and the Holy Sword to create the exact type of singularity he want, while Dark Era, Stormbringer and 55 Minutes go about how contradicting singularities are unpredictable and often result in something completely different from the abilities they originate from.

You got what I mean, right?

In Stormbringer, N said abilities are tied to the users' soul, so if we apply this theory to BSD, whenever an ability user dies, their soul remains and their skill follows said soul to the new body, we even have Dead Apple and 55 Minutes to show how skills are also sentient!

Not only that, he said singularities were mistaken as gods or beasts' work in ancient time, that's why Verlaine and Chuuya's singularities are named after the mirrors of beast and god: Demonic beast Guivre and Destructive god Arahabaki.

But wait, Atsushi's ability Beast Beneath the Moonlight allows him to transform to a white tiger, if you go to the internet and do some research, you will find tons of Chinese and Japanese legends about the white tiger, aka Byakko.

Could it be, Beast Beneath the Moonlight is indeed a god in ancient period, for it to always sticks with Atsushi's soul, so Fyodor who is around 600 years old, could find the orphanage he was in and tell Shibusawa of the boy?

The parallel which Byakko-Draconia has with the white tiger and the azure dragon, two of the four Holy Creatures in Japanese folklore is remarkable.

And again, Fyodor somehow knows to awake the dragon singularity.

[vii0so]

[ BSD 124 Spoilers ]

Thoughts, Theories and Analysis

This was typed and meant to be posted the same week the update came out but instead it's been collecting dust in my drafts because I've been busy and haven't had time to continue it. I remember wanting to go more in depth on topics.

Anyway, since the update will be out tomorrow, I'm posting it. Be aware, I haven't checked what I wrote, so if it looks like a point was abruptly stopped or something doesn't make sense it's because of that.

-

Firstly and most importantly, it's not over, nothing ever is with this story. The only thing over is Ueda's suffering and guilt.

This part, Ame-no-Gozen, may be over (or maybe not) but just because a pawn has been captured doesn't mean it's checkmate. Fyodor is still out there, the battle isn't over.

Secondly, Akutagawa did die...I'll explain.

Akutagawa's head was crushed and so he died. In the last chapter I assumed he wouldn't stay dead, just like all the others killed by Ame-No-Gozen who turned into bubbles. Surprisingly, this wasn't exactly the case. Akutagawa never even got to become bubbles.

In one part, Atsushi says the following:

Basically, once the space breaks, all the people trapped inside (the people killed by ame-no-gozen who turned into bubbles, as well as Atsushi and Ueda) will be free and therefore alive.

This is great and I expected it...but something I didn't expect was that on top of breaking the space itself, he also travels back in time to before Akutagawa's death to save him.

The time travel wasn't the unexpected part, the director literally explained that Atsushi could move between past and present in that space, so it was bound to happen.

But if Akutagawa was going to bubble anyway, then once the space was broken he'd be fine again...so why travel to before his "death"?

Also, side note, this may just be me, but I find it interesting that the time travel was shown to us in the form of a static screen...actually, the more I stare at it, the more it looks like scribbling out a scene in pen, which makes more sense too:

Anyway, before I try to answer the "why travel to before his "death"?" let's think about the "what does this mean?".

Time travel is finicky and all authors, stories, and plot conditions make time travel have different outcomes and effects.

There are many ways time travel may work, here are a few:

Creates an alternate timeline, erasing the previous one. -1 +1

Creates an alternate timeline and the time traveler ceases to exist in the previous one but the timeline continues to exist. -0 +1

Rare case that only works under specific narrative conditions: The time traveler was always meant to go back in time and change stuff, therefore the timeline remains the same. -0

The amount of time traveled also makes a difference to the timeline; luckily, in Atsushi's case, it was only minutes.

One common factor about time travel (except in a few rare cases) is the fact that:

Time travel creates alternate / branching timelines.

Let's backtrack a bit:

In an old post of mine, back when we found out Atsushi was the "bookmark" and I tried explaining what that meant, I said this:

Well let's start simple: "What's a bookmark?" It's an indication of where you left off in a story. In a game, you could think of it as a [save] point.

The bookmark would be the only way to progress in a story. The only thing telling you where the 'present' is. Time is divided in three: Past -> Present -> Future Q. Where is Atsushi? A. The present No matter wether he could time travel, or we read chapter 1 again, he will always be experiencing it 'currently'/in 'present time'.

At the time, I myself wasn't sure how to explain it properly and tried to explain my thoughts as best as possible. Surprisingly, I was technically right!

To paraphrase and add a bit:

Atsushi, as the bookmark, represents the present. Time travel is possible because no matter where in time Atsushi is it'll count as present time, just like a bookmark in a book, he marks what page we're on.

Now...I don't know how many of you reading this have ever read any Gamebooks like 'choose your own adventure' or played any Visual Novels with choices and different routes and endings, but I'll be using them as a way to further explain, so I'll try to explain a bit about them.

In a Gamebook, while reading, you are given choices, for example:

In an attempt to find out where the sound came from, you run towards the hall. Just as you enter, you see a lady running down the left corridor, screaming about a ghost. As you're about to follow her, you see a ghost floating down the corridor on your right, towards the garden. Who do you want to follow?

If you want to follow the ghost, flip to page 56

If you want to follow the screaming lady, flip to page 82

You then go to the page, read until another choice appears and eventually reach one of the endings of the book.

A Visual Novel (VN) has the same concept as a Gamebook but is a video game with pictures and music, along with words. Some are more like plays (more dialogue and inner thoughts) while others are more like novels (more descriptions, paragraphs and only necessary dialogue).

One thing in common with both VNs and Gamebooks is the way the reader/player always has to make choices that lead to different situations and/or endings. They're interactive, with branching routes, bad and good endings.

Another thing they have in common is a bookmark.

A Gamebook is an actual book and therefore a bookmark can work with it easily; just put it between the pages to save your place. You choose to follow the ghost and flip to page 56? Ok, the bookmark is now on page 56. You want to go back and follow the screaming lady instead? Sure, the bookmark is now on page 82 as if you never followed the ghost. We control the bookmark to mark where we're up to, what the 'present time' in the story is to us.

In VNs it's slightly different. A choice appears that may branch the timeline? You have to save that instance to a save slot. A few dialogue boxes later you realise you should have picked the other option? You load your save from its save slot and travel back to the option again, like nothing in the other timeline happened, erased.

Both of these examples are great. Visual Novels loading and overwriting save files, therefore erasing that timeline (even if the possibility of it still existed in the branches) and Gamebooks that use a bookmark to mark the present timeline, choice after choice, and jump between them.

Now, when it comes to Atsushi as the bookmark, the similarities can help us understand how time travel was used in this context, and so, we can figure out what happened to the previous timeline.

Placing the bookmark back (loading a save) makes it so anything that happened after that, never happened. Therefore the new timeline becomes the only timeline and the old timeline is erased, overwritten, and ceases to exist.

Even without the bookmark deep dive, just considering the scribbled out effect to show the time travel, it lets us imagine the previous timeline being scribbled out, erased and rewritten.

So yes, in the old (now erased) timeline, Akutagawa died. But that him has now ceased to exist and this him is the only existence.

Also, while the previous timeline was erased, it doesn't change the fact that this is now a different timeline, where Akutagawa never saw the Dazai hallucination as he was never in a near death state by Ame-no-Gozen before being killed. I'm actually a little upset by this...like, don't get me wrong, I'm glad he's alive, but his near death hallucination experience felt like a needed moment of weakness (in a positive he-finally-shed-a-tear way) and weird form of acceptance, and now, the current him never got that.

I guess it makes sense though...if you're only reason to live is to seek acknowledgement by proving yourself through fighting and basically wanting to be told you've fought enough, that your effort wasn't for nothing, that your life had meaning, then why live past it and not accept your death when it's right there? If he lived past that, do you think he'd have the same resolve to live and fight? The reset meant never getting what he wanted, and that was the only way to keep him going.

Also, I think I saw someone mention how Atsushi saw Akutagawa's Dazai hallucination and that's why he Thanos-snapped the timeline. I get that it was probably just a headcanon, but I'm just going to mention it here in case anyone was genuinely confused: Atsushi did not see anything.

Even if Atsushi could magically see other people's hallucinations, there just wasn't enough time. Atsushi looked out onto reality, saw Akutagawa for a second, witnessed his death, and then shouted his name, no indication or enough time for him to see anything.

Anyway, let's quickly talk about where the new timeline starts:

On the left we have the erased timeline (Chapter 123.5) and on the right we have the new timeline (Chapter 124). Both panels are of the same moment.

Akutagawa's left arm still bubbled, it's just that at that moment in the new timeline, Atsushi suddenly appeared from the dead and took Akutagawa's full attention instead.

That's the first difference in the timeline.

---------------------------------------------

So why travel to before his "death"? idk (maybe I knew while writing this all in the start but I didn't write any note for myself)

---------------------------------------------

I was initially briefly confused by this. Was the Ame-no-Gozen we knew actually Tsuki-no-Gozen or was the sword used to remove Ame-no-Gozen's life force Tsuki-no-Gozen?

The answer: The sword used to remove Ame-no-Gozen's life fore: Tsuki-no-Gozen.

It pulled out Fukuchi, who was Ame-no-Gozen's life force, essentially killing it. We can even see Ueda holding the sword and the difference being clearly shown.

[mayoi-inu]

This is getting interesting :)

So the two blades are named after Ueda's ability.

雨月物語　Ugetsu monogatari, Tales of rain (雨) and moon (月)

But also one of them manipulates space time and the other, the one for the moon, manipulates life force.

The moon is related to Atsushi's ability beast under the moon. His ability is regeneration.

And the rain is related to Akutagawa's ability! Have you read Rashoumon? Rain and cloth.

Ahahhhhahahahaha

[pe4rl-diver]

i don’t think amenogozen is truly killing people

remember how teruko melted and all that was left was her hd uniform?

the hunting dogs took her in, gave her a home, gave her a real purpose. that uniform represents who she is.

but when kunikida melted, his clothes went with him, and what was left behind instead?

his notebook. his ideals. his ideals represent who he is.

the thing that represents who they are is left behind.

i know that doesn’t really explain anything, but it’s at least enough for me to cause some doubt

[sorcerersandskillusers]

Spoilers for Chapter 114.5

This confirms that Dazai is literally the only person who can kill Fyodor since he would nullify the possession. Which makes the "You can't kill me line" way funnier because Fyodor was really thinking

"please for the love of god do not be the one to kill me"

[featherstorm2004]

Ok but the implication that Fyodor inherits the personality traits of the people who kill him is extremely messed up when you think about it. And considering how old he is it's very likely his original personality has been completely taken over by this point, honestly I wouldn't be surprised if Fyodor doesn't actually have a grand master plan but is instead working with a hodgepodge of half baked ideas culminated by his past vessels over the centuries.

Especially when you consider that these new desirers seem to effect him strongly, with him not giving two shits about Aya until he took over Bram and now suddenly he's yandere levels obsessed with her.

[justcallmesakira]

I love how the bsd fandom was celebrating chuuyas birthday being happy, joyful, a bit of angsty JUST yesterday and then fyodor just comes to ruin the party like that one auntie that no one of the family likes.

[loulits]

There’s something so fascinating about the dynamic between Dazai and Ranpo that rarely gets the attention it deserves.

Their relationship isn’t built on the same kind of camaraderie we see with Dazai and Chuuya or Ranpo and Fukuzawa. Instead, it exists in this weird, nebulous space of mutual brilliance, calculated detachment, and an unspoken understanding that neither of them really need to try around the other.

Both of them are geniuses, but in very different ways. Ranpo’s intelligence is so deeply ingrained in his identity that he doesn’t even consider it a “gift”—it’s just who he is. His self-confidence is absolute, bordering on arrogance, because he knows he’s the smartest person in the room. He doesn’t second-guess himself because, in his eyes, there’s simply no reason to.

Dazai, on the other hand, is an entirely different breed of genius. His intelligence is adaptive, shaped by his time in the Mafia, honed for manipulation, survival, and deception. He’s brilliant, yes, but he’s also deeply aware of his own mind—sometimes to the point where he actively tries to outmaneuver himself. Where Ranpo is unwavering in his certainty, Dazai constantly tests and plays with possibilities, viewing life as a game where he’s always five steps ahead.

That’s where their dynamic gets interesting. 🤨 👇🏽

1. They Don’t Need to Prove Themselves to Each Other

Dazai is someone who loves testing people. He provokes them, plays mind games, and watches their reactions for fun. He enjoys unraveling people, poking at their insecurities, seeing what makes them tick. And yet, with Ranpo? There’s none of that. Why? Because Ranpo sees through him. Where most people get caught up in Dazai’s theatrics, Ranpo just doesn’t care. He can see the games Dazai plays, but they don’t interest him because, in his mind, he’s already won before the game even began. This puts them in a strange but mutual space of respect—Dazai doesn’t bother trying to manipulate Ranpo, and Ranpo doesn’t feel the need to prove that he’s smarter. It’s one of the rare relationships where Dazai can just exist without putting on an act.

Image Source: Unknown

2. Dazai as the Observer, Ranpo as the Unshakable Constant

Dazai is constantly watching. It’s in his nature. He studies people, picks them apart, and predicts their next moves before they even think to make them. Ranpo? Ranpo doesn’t need to do any of that. He simply knows. This makes for an interesting contrast because, while Dazai is always looking for the angle, Ranpo just goes about his life, unbothered. He isn’t someone that Dazai needs to figure out, and that in itself is probably a little unsettling for Dazai—Ranpo is just Ranpo. There’s no hidden agenda, no underlying deception, just unshakable confidence in his own abilities. At the same time, I think Ranpo finds Dazai mildly interesting in a way he doesn’t find most people. Not because Dazai is a challenge—Ranpo knows he can see through him—but because Dazai operates so differently from him. He’s amused by Dazai’s schemes, the way he plays with people, but he doesn’t feel the need to engage. It’s almost like watching a child play with a puzzle you solved years ago.

3. A Quiet Understanding

Ranpo and Dazai don’t need to be close. They don’t need dramatic moments of bonding or grand declarations of friendship. Their relationship is more of a quiet, mutual acknowledgment—one genius recognising another, but with no need to test the limits. They don’t challenge each other. They don’t need to. And maybe that’s why their dynamic is so compelling. They just understand.

[with-my-calamitous-love]

i see so many chuuya fics where he’s a player/a womanizer. and while those are all fun and beautifully written, i just have this gut feeling that chuuya is loyal as hell.

this is the guy that jumped off a helicopter and fought a literal dragon for a man he claims he doesn’t even like. imagine what he’d do for someone he loves, someone he has yet to lose and is terrified of losing.

all he wants to do is love you. he’s protective, but not possessive by any means. his time in the mafia has made him so aware of everything that could possibly harm you. even if its a 5 minute walk back to your place, he’ll drive you. if you’re out at a bar, he’ll hold your drink and/or keep an eye on all the other guys around you. he’s always practicing the sidewalk rule, always giving you his coat, and always reminding you that he would do anything and everything for you.

he knows that you’re a point of interest for enemy organizations. that because your his s/o, you’re a target for ransom or worse as a means to get back at him. and because of that, he’s constantly worrying. if even something feels off, he’ll call you, if not rushing to be by your side. you have to remind him that you aren’t made of glass.

oh, and god forbid you are actually taken captive. the world will see a side of him that he luckily keeps hidden.

[symphonyofsilence]

We don't know much about Dazai's life before Mori found him (just that the sheep had offered Dazai to join them and he declined)

But in "Dazai, Chuuya, age fifteen" there might be some clues:

He talks as if he previously hasn't been a part of the underground society. Like he's lived in the surface world.

His mannerism in general, even as a 15 years old is so refined. And the manner of his speech is different from the 15 y/o kids who are from the underground society like Chuuya and Shirase.

And the characters are heavily inspired by the real life authors that they're named after. Dazai already has so many things in common with the real Dazai Osamu. And the real Dazai Osamu was from a noble family.

So I think it's likely that Dazai was from an upper class family and ran away.

And... I think it's not completely unlikely that he might have changed his name.

in BSD, when a character is inspired by and named after an author who has a pen name, their real names are addressed. Like Mori Ougai being called Rintarou by Elise, or Fukuchi Ouchi being called Gen'ichiro by Fukuzawa or Dazai calling Oda Sasunosuke Odasaku, or 'Nakahara' being revealed to be the last name of the doctor who worked on the Arahabaki project and thus being Chuuya's "father" and so his last name being Chuuya's last name, while it's revealed that Chuuya might have an actual family out there, we don't know much about them but his father has the same occupation as the real Nakahara Chuuya's father; he's a retired army doctor who has established his own clinic. And the real Nakahara Chuuya was at first 'Kashimura Chuuya' before his father was adopted by his mother's family shortly after Chuuya's birth and his name was changed to Nakahara. Now maybe BSD's Nakahara Chuuya's real father's last name is Kashimura and thus before the age of 7 and merging with Arahabaki, Nakahara Chuuya might have been Kashimura Chuuya.

What I was getting at was that... maybe BSD's Dazai Osamu's real name is Tsushima Shūji (like his namesake, the real author) but he changed it after he ran away from his rich family and joined the underground. (But this theory might not work because Ranpo's namesake, the real author used a pen name too but Ranpo Edogawa seems to be the real name of BSD's Ranpo.)

[kellelkallel]

I think people forget that Dazai controlling his heart is not just a one-off thing. Like he totally does it all the time.

The whole of the Prison Arc? That poison would've killed him way slower than Dostoyevsky by virtue of him making his heart incredibly slow, so it spreads slower. That's why he can afford to take his time with shit.

When he gets shot/stabbed multiple times? He can slow that shit down and lose less blood. He's so smart I love my little freak boy

[literatureloverx]

Hii! I'm new here, but I'll just get to the point. I want to know your opinion about something

I've heard a lot of people saying that Dazai would cheat on his partner. I know it's not true, but I just wanted to know your opinion about it

Have a nice day!

I do like people who just “get to the point”. ♥️ First of all, welcome to the family! Second, I don’t think so at all.

Dazai is not a bad person. The only scenario where I could see him being unfaithful is if he were afraid of emotional intimacy (which I think he would be) and tried to push his darling away. Though, even then, I am not sure he would actually go through with it.

Given his self-sabotaging and self-destructive tendencies, it is possible, but whether he would genuinely cheat or merely create the illusion of it is open to interpretation. His desire to distance himself from his darling would likely stem from his idealised view of them, believing he doesn’t deserve them because he sees himself as tainted.

However, in my opinion, Dazai genuinely wants to improve because he is exhausted by the constant emptiness he feels. Let’s say he has a darling who fills that void inside him—would he truly want to let them go? I believe he would only push them away under specific conditions, such as self-sacrifice, driven by the need to protect them from the inevitable consequences of being involved with him—both because of his dangerous life and his internal struggles.

That being said, considering how Dazai thrives on manipulation and control as well, even if he were to push someone away, it might not be purely self-sacrificial. It could also be a subtle test, a way to see how much they are willing to fight for him. (I somehow love how hypocritical he can be. The poor man is so stuck—please, someone shake him and tell him, “We can do this together.” 🥺 He is so lonely.)

Though, I think this is an extreme scenario, one where he is 100% invested in someone, particularly romantically.

I hope this answers your question. Have a nice day as well! ♥️

[ghostlytragicangel]

Listen batshit insane theory that Fyodor is the broken sword while Atsushi is the time sword.

This is gonna sound crazy but I'm gonna keep going.

Which could be why Fyodor is looking for his other half because the swords were called the twin swords which could be why he had originally thought that Dazai was his other half and could be why Fyodor seems to know so much about Atsushi.

Remember that one chapter where Atsushi has a sword going through his head and Amenogozen also had a sword go through their head so what if the sword going through Atsushi's head wasn't really a hallucination but a projection from the time sword.

And in 55 minutes Atsushi was called the foreseer and travelled through time.

[lukeria314]

“And if dreams can come true — what does that say about nightmares?”

People who say that Chuuya must be able to dream are deeply mistaken and forget that he is an experimental project, whose life was sustained by liquid—and his REM phase wasn’t just reduced, dreams were eradicated from his brain entirely. He had no foundation upon which to build dreams. He lived in that tube like in a coma, unaware of anything except the fluid around him. His associative imagery simply didn’t form. He is blind in that regard. They took him as a child, and until adolescence, he sat in that tube with no memory of himself.

He doesn’t know how to dream. He has no reason to dream. He simply has nothing to dream with.

He may have developed chronic REM-sleep disorder because he never had a proper sleep cycle in the first place—it never developed and possibly never engaged afterward either. And without REM sleep, there are no dreams, even if you’re asleep.

Moreover, Stormbringer openly reveals Chuuya’s struggles with his sense of self. “Who am I?” And that “I” is the core of dreams. There are no dreams in which he could participate. He is like a newborn. He sleeps like a machine, just a robot. He has no dream-related brain activity. In this sense, he’s an eternal child.

The fact that he spent his entire life in a test tube also affects his height and weight. Starting with the basics: the body has no stimulus for growth. In fluid, under weak gravity, muscles and bones have no resistance to develop against. They simply don’t develop. On top of that, growth hormone is released during sleep. And as mentioned above, Chuuya didn’t sleep in the conventional sense—his state was closer to a coma.

Also, some of the hormones necessary for growth and development are produced through movement and proper nutrition. When a person doesn’t eat, doesn’t move, and doesn’t follow a circadian rhythm, hormonal signals become disrupted, and growth hormone production is suppressed. Add to this the fact that the cells don’t regenerate. Surrounded by fluid, with no oxygen, no micronutrients, no proper blood circulation or metabolism—cells can’t renew, be nourished, or receive the signal to grow. Hormones aren’t produced. Tissues aren’t stimulated. Nothing applies pressure or stretches them. Even if cells do divide, they remain in a suspended state, because without external stimuli, they don’t differentiate into specialized cells. They don’t mature.

In biological terms, all growth signals are dulled.

Now, seventh-grade physics: a body immersed in liquid is subjected to uniform pressure from all sides. Depending on the depth and density, this pressure varies. The fluid balances out the internal pressure of tissues—essentially creating resistance. This means tissue doesn’t “push” against its surroundings, because everything is compressed back. There is no space for growth. In fluid, as mentioned earlier, there’s no gravity. The body doesn’t know where up or down is. But all organs and bodily systems grow with orientation in mind. Without it, spatial awareness is lost.

And do you know why Chuuya’s mass might appear larger? Let me repeat the blobfish analogy. If the liquid he was suspended in was dense, then once he’s taken out onto dry land, where the pressure is different and the fluid no longer compresses his body, he would swell—only slightly, but still swell.

And to top it all off: asymmetry. The body stays stuck in one position. This leads to deformed limbs, a crooked spine, underdeveloped joints. The skin becomes thin, with no developed protective horny layer, leaving the body vulnerable to infections. Bones, without stress or load, become thin and soft—even hypoplastic. They never gain proper shape or density; they’re weak. The body was essentially preserved. Now, he has narrow lungs, potentially inverted organs (due to lack of gravity orientation), and even his face remains childlike.

It’s abnormal. It’s miniature. It’s asymmetrical.

People always overlook the key fact: no matter what kind of person Chuuya is, he’s still a child, subjected to experimentation by grown men—robbed of everything a “normal” child or human of his age is supposed to have.

[vii0so]

[ BSD 123.5 Spoilers ]

Thoughts, Theories and Analysis

Literally forgot a new chapter was even releasing today but holy shiz today's update was great. I love it, especially this part:

My heart can't take thiiiiis! Would it be strange to say I'm glad we saw Akutagawa cry? Like, I'm happy for him, it's like a weird form of closure / acceptance for him.

He's not dead dead obviously. Just like all the other characters 'killed' by Ame-No-Gozen once this whole ordeal is over he'll retuen.

Honestly, even before the ordeal is over he will return and fight alongside Atsushi (as we see in the look ahead of the anime's last ep). Probably with Ueda's help.

I doubt Atsushi will actually kill Ueda. It's not that I find him too soft to kill, quite the opposite, he can and will kill depending on the situation and the type of person, but Ueda is not a bad person, they didn't want any of this to happen. Ueda is someone who has basically been imprisoned and forced to watch their creations be used for evil. They witnessed one die (destroyed) and now they are witnessing the other one be used for destruction without anyway to stop it.

Thus, Ueda wants to die as a way to free their creation from its fate and themself from this eternity of guilt and suffering in captivity.

To me, this part sounds like a parent who's twin children were turned into weapons of war. They gave them the gift of life only for their life to be turned into a weapon used against anyone the wielder saw fit. Eventually, the parent - seeing one of their children die from wear and the other forced into continuing the same mindless slaughter - can't take it anymore and wishes that they had never brought them into this life.

Random fact: Ame [ 雨 / あめ] means rain and Tsuki [ 月 / つき ] means moon - a reference to the real author's work - and therefore the bsd character's ability - "Ugetsu Monogatari" (Tales of Moon and Rain).

Anyway, back to Akutagawa, how is he seeing Dazai? For Atsushi's case we got the explanation that it was basically created by his mind under the influence of Q's ability. This is then immediately confirmed.

But what about Akutagawa? Even if he had been affected by Q's ability, the mental burden taking effect only now would be strange.

The most likely possibility is some form of the near death effect, where people who are about to die may see their loved ones (usually deceased family members) telling them words of encouragement and things along the lines of "you did well" and "it's time to go" or even the opposite, such as "it's not your time yet".

So after openly thinking that this would mark his end, his mind conjured up Dazai because a part of him remembered what Atsushi told him about.

Honestly, the strangest part of this whole thing for me was the music. Most people probably didn't think about it much but to me it seemed strange.

If he first saw Dazai and then heard him speak I could say that in his state of mind his brain created an auditory hallucination. But the music starts while his eyes are closed, before he even sees Dazai.

"Atsushi could hear his hallucination while he was asleep."

Yes, but Atsushi's "shadow" was created by his mind under the influence of Q's ability, not as a near death 'these are my final moments' brain response.

Maybe I'm thinking into this too much...music is definitely possible if it was a strong factor from a point of time in his life. Does this mean Dazai has played the piano for Akutagawa or that this is a melody that left an impression on him in some part of his life similarly to Dazai? Maybe neither, maybe both, will we ever know, does it mean anything at all? ...yeah, I'm overthinking this.

Btw...am I the only one who wants to know what song was played?