Yankee High School Girl 1~ Ibaraki's Strongest Legend (2008)

Umihisa (Rio) had become the leader of the Ibaraki delinquent world, but because her father had been cheated out of all his assets, she decided to leave the delinquent world and transfer to the same prestigious school where her cousin, Hitoe (Minami Aiyama), attends, aiming to marry a rich man. However, instead of changing her attitude, Umihisa goes to school in a delinquent girl uniform from the 80s, spits on her teacher, and behaves badly... Then, Hitoe goes missing!