Tsushima Sakura Ki, male, seventeen years old.
A self-taught sorcerer, the boy owns nothing but a pair of differently colored eyes that can see curses and a body that can nullify cursed energy.
When he was fourteen, something resembling a screen appeared before him, though no one else could see it.
Perhaps it was the hypocrisy of an outsider, or perhaps it was because the boy on the screen had a pen name identical to that of his favorite author. Whatever the reason, he revealed his existence when the boy was suffering over what he had learned about the future.
From then on, he sank deeper and deeper, unable to pull himself away.
Dazai Osamu had always searched for the meaning of being alive. After accidentally learning the truth about the world and losing his closest friend at fifteen, he found the answer even harder to reach.
It was then that he heard a boy's clear, gentle voice.
And he kept hearing it for years.
Severe out-of-character portrayals, lots of original headcanon.
Jujutsu Kaisen timeline is set before Geto Suguru's village massacre.
I'll add more when I think of it.
Theme: If it exists, then it is reasonable.