Куросакі Рюїчі

Ryuuichi Kurosaki is a delinquent guy whom Yoshiko Hanabatake interacts with and he becomes her disciple, calling her big sister. When Ryuuichi first appeared, he was shown to be just your typical delinquent. However, after meeting Yoshiko Hanabatake and Akuru Akutsu, he became a lot nicer and shows his idiotic side more.