Kumiko Yamaguchi, a bright and eager math teacher, steps into her new role at Shirokin Academy only to find a chaotic environment filled with troublesome students and intimidated staff. Unbeknownst to her unruly class, Kumiko conceals a powerful secret – she is the heir to a yakuza group with formidable abilities. Balancing her criminal background with her teaching duties, Kumiko must navigate the challenges of concealing her strength from her students and the watchful eye of the vice principal, all while facing suspicion from Shin Sawada, the rebellious leader of her delinquent class.