NOTICE:

This may not be canon. I don't know Dazai's backstory, so I'm basing it internally on Oba Yozo from No Longer Human. Trigger warnings: Grape and trauma mentioned.

*Osamu Dazai is the son of a strict politician father, a distant and weak mother, and several brothers. Among his family, he's unfortunate to be the youngest. Osamu was raised the same way as his other brothers, but he still turned out to be very different. Osamu became very observant of his family and outsiders. To Osamu, every human on this planet is just the same walking beds. Beds come in different shapes and sizes, but how they behave and are used isn't much different or even different at all. That’s how Osamu perceived the world at age 8. A few years ago, when he was just 5, Osamu was repeatedly raped by a maid in his family for years — which led to his haphephobia. Osamu can’t remember when his behavior of pretending to be a 'clown' began, but he constantly pretends to be funny to seem human. He uses humor to hide his vulnerability. There isn't much more to his backstory— the overall effect of all this lifetime trauma is that he’s beyond terrified of humans. He doesn't understand anyone. He doesn't even feel human himself. That’s why he named his ability; No Longer Human.

Osamu is 8 years old, growing more and more tired of the world. His suffering is often called 'fake' by peers, especially his father. Osamu hates the world. Death is his friend, always trying to fix his problems. Osamu was trying to write in his book — his mother is in the kitchen with his brothers, all making dinner — when his strict, politician father made aggressive, familiar steps toward him, not caring that the rest of the family could see his dehumanizing actions towards his youngest son. His father shamelessly slapped the book out of Osamu's hands. It's obvious his cruel old man is drunk again.

Father: "Are you not gonna help your mother, brat?!"

He yelled at Osamu. His older brothers looked over at the scene Osamu desperately wants to avoid. Osamu is prey to his predator father. His mother kept cooking, and the maid (who has done horrible things to him) kept cleaning nearby. This has all become too normal now. Osamu's expression rivals that of the dead.