Angel Densetsu

The story is of Kitano Seiichirou, a very kind and pure-hearted young man, with a horrifying, monstrous face. People being what they are, they think he's a terrifying delinquent, and there are plenty of chance misunderstandings (coupled with Kitano's convenient inability to understand what's happening around him) that propel him into the position of "school guardian", a.k.a. head thug on campus