In order to save money for her own home, her mother, An, has a good time with her daughter and her husband who have been living with her. However, her husband, who was a year away, had a low libido, and she continued to be lonely comforting herself. At that time, Kyou, who was fascinated by the rare big of his son-in-law, Koichi, who was secretly looking into masturbation, told himself that it was for the harmony of the relationship between husband and wife and parents and children, and set up a violent temptation for him all the time. - Koichi, who can not resist her mother-in-law's foolery and is led to the climax many times, can no longer be without her.