Kumiko Yamaguchi is intelligent, energetic, and prepared to begin her dream position as a mathematics teacher at Shirokin Academy. However, when her first day reveals terrible students and frightened teachers, Kumiko understands that the all-boys high school is a hotbed of delinquents who have no desire to better themselves. Yet, what her unruly students are unaware of is that beneath her nerdy exterior, Kumiko serves as the acting head of a powerful yakuza clan, and she possesses the skills to demonstrate this! Able to subdue even the toughest gangsters in mere seconds, Kumiko must conceal her immense strength and criminal connections to retain her employment. Regrettably, with the vice principal persistently attempting to have her dismissed and Shin Sawada, the leader of her delinquent class, suspecting she is more capable than she appears, Kumiko faces a challenging teaching career ahead.