Crows Zero

Kurôzu zero is a movie starring Shun Oguri, Kyôsuke Yabe, and Meisa Kuroki. A transfer student attempts to take over the most violent high school in the country, whose students form factions and battle each other for power.
The students of Suzuran High compete for the King of School title. An ex-graduate yakuza is sent to kill the son of a criminal group, but he can't make himself do it as he reminds him of his youth.