Koharu is asked to tutor her student Chika, who has been misbehaving. However, Chika is the mistress's daughter of a high-ranking yakuza member, and the school itself is secretly tied to the yakuza, running an underground club. One day, Koharu is suddenly kidnapped and imprisoned in the secret club. She is no longer treated as a teacher or even a student, but instead forced to perform as a sex slave in live shows. Trapped in this isolated chamber, how will Koharu confront the horrors of her new reality?