A high school teacher, Rina, who has been married for 5 years, seemed to have a happy life on the surface, but in reality she was dissatisfied with her husband's sex with her and wanted to masturbate alone. Was met. One day, her sister, Aki, brought her fiancé. The other party was a student, Sumio, who was held by a new teacher, Rina, to be fucked in an empty classroom. Rina tries to avoid Sumio as much as possible, but he does not allow it, and opens the gap to reach Rina's body and asks for the old relationship. And while Rina is away from her husband, she goes crazy by her sister's fiance, becoming a lewd sister....