Mainly Jujutsu Kaisen: I Heard I Used to Be a Shinigami

Ichimaru Gin, former captain of the Third Division, reincarnated after death as a five-year-old with no memories. He looked like nothing more than a silver-haired little dumpling, too weak to hurt a fly.

After spending a year in the world of jujutsu, he was hauled off to Jujutsu High by Gojo Satoru and Geto Suguru, back when they were students.

Gojo: Suguru, look! This kid looks exactly like me!

Geto: ...

Utahime Iori, pointing accusingly: Gojo, has the Gojo family finally driven your illegitimate child out into the world because of your scumbag behavior?

Gojo: ? I'm still a virgin, thanks.

CP: Aizen x Gin, Gojo x Geto. Severe OOC warning.

Theme: Even if reason makes you hate me, instinct still draws you close to me.