Haruo's wife, out of concern for her mother-in-law Ayako after the loss of her husband, continues living with her. Ayako, grateful toward her daughter and son-in-law, maintains a peaceful relationship with the couple. However, one day, Haruo accidentally catches Ayako deeply engrossed in masturbating. The sight leaves a powerful impression on Haruo, and from that moment, he finds himself uncontrollably aroused whenever he sees Ayako. Eventually, Haruo reaches his breaking point and can no longer hold back.