I'll Let You Use Extracurricular Classes.

Ikuko, a teacher at a part-time high school, is tied up by three men in the physical education club's equipment storage area in the basement. Her husband, Ichiro, works as a private tutor, but he continues to have an affair with her former student Toshiko. Ikuko was informed of her husband's affair by her student Inoue, and she was also told that she was one of the people Inoue had sex with. She was then invited to the basement of the school, where she was asked to listen to her concerns. Two of Inoue's friends are also waiting in the basement, but Ikuko is secretly planning something...