Yamaguchi Kumiko, a new teacher at Shirokin High School, has been assigned to teach a class full of the school's most notorious delinquents. Unbeknownst to her fellow teachers, Yamaguchi is better equipped to deal with her rowdy students than most: as the granddaughter of the head of the Oedo family, she grew up around yakuza gang members and has learned to fend for herself. When one of Yamaguchi's students, Kumai, is accused of stealing a bag of money from the head teacher, she is forced to intervene to keep him from getting expelled. But is he really as innocent as he claims to be?
