Ware wa ken-ou!! manga

Ware wa Ken-ou!! summary:

Yoshiaki is entering a school that is famous for its fights and violence. He chose to go there for just that reason, and he intends to be the strongest one there. When he first arrives, he helps out a girl called Homura, who is being picked on by some guys. When she asks him to be her "sword" afterward, Yoshiaki doesn't know how to respond. Apparently, students of the school team up in pairs; a "sword" and a "master". Others advise him not to associate with the girl, who is a "Rank F", as she probably won't live very long. However, Yoshiake is not thrilled with the idea of abandoning her to die.