Kumiko Yamaguchi is bright, upbeat, and eager to begin her dream job as a math teacher at Shirokin Academy. But as her first day begins, Kumiko finds that the all-boys high school is a quagmire of delinquents with no intention of better themselves. What her boisterous pupils don't realize is that Kumiko is the acting leader of a major yakuza clan, and she has the ability to prove it! Kumiko, who is capable of defeating even the most powerful criminals in seconds, must keep her amazing strength and criminal influence hidden in order to preserve her job. Unfortunately, with the vice principal constantly trying to get her fired and Shin Sawada, the leader of her class of delinquents, suspecting she's stronger than she lets on, Kumiko has a difficult teaching career ahead of her.