Kill Blue

Synopsis

Juuzou Oogami's a legend. Even among hit men, his name sends shivers down their spines. There's never been a job he couldn't handle—that is, until the day he awoke as a teenager! But how did his body transform? To find out, he'll have to infiltrate the one place he never thought he'd find himself in...school! (Source: VIZ Media)

Anime adaptations