Well if you're an average ordinary person like Yuu, you're probably going to Purgatory. Every soul is "planted" there, and it's growth measured. If it stays the same, you stay there. You can leave though! In order to ascend to Heaven, you have to grow your sprout and make it bloom! To make it bloom you have to...
Work! And lots of it!
Yuu works at Purgatory Post. It's a postal service that serves both Heaven, Hell, and Purgatory (and on occasion, Earth!) Yuu has to deliver mail across these dimensions, and through which she has to deal with all sort of monsters, creepy crawlers, and Abberations. That's okay though! She's got her trusty Mailbag! She's soul bonded to it, and because of that, any mail the bag eats gets she receives a power (and new look!) based off the message contents!
Crazy right?
I hope to share more from this world soon, and I hope you'll join me next time to introduce Iris, her boss!