Sakigake!! Gokudo Yankee Gakuen

Original title: 魁!!極道ヤンキー学園

Ryoko, a high school student, is the heir to a yakuza family, but keeps it a secret at school. One day, Shijo, a delinquent who got into a fight with the yakuza, goes missing, and Shinichiro, who tried to help Shijo, is kidnapped as well...