Riko Akasaka

The only daughter of the Akasaka dojo. Originally she visited another senior high school than Mitsuhashi and Itou, but ultimately decided to transfer to Nanyou High instead to repay Mitsuhashi's favor. Being pretty skilled in Aikido, she can handle most delinquents on her own despite her small body size and harmless appearance.

While she used to be very popular at her old school, in Nanyou High she is considered somewhat weird because of her constantly hanging out with Mitsuhashi. As the manga goes on, her originally quiet personality gradually changes, due to Mitsuhashi's influence, to a brighter version of herself. She has a crush on Mitsuhashi and is the only person who refers to him as "San-chan".

(Source: Wikipedia)