Satomi Nagasawa was sexually trained by her high school homeroom teacher, Mr. Sawada, who summoned her after class throughout her school years. Ten years after graduation, now happily married and living as a devoted wife, she unexpectedly runs into Sawada, who forcibly drags her back to his house. From that moment, her life changes completely as relentless, snake-like BDSM training begins anew. Tormented by disgust and guilt, Satomi gradually succumbs to the long-forgotten pleasures of her masochistic desires, writhing in ecstasy as she falls into a double life—sharing passionate sex with her husband by day and serving as Sawada's obedient M slave in secret.