Mitsuko's daughter had gotten married and left home, but because both husband and wife worked, housework was too much work for her, so Mitsuko and her daughter and wife decided to live together. Mitsuko had been single for a long time and was frustrated, so she couldn't stop satisfying herself. One night, when Mitsuko went to the living room, she found her son-in-law masturbating on the second floor, even though he was supposed to be sleeping with her daughter. The two of them became awkward after seeing this. When they heard what he had to say, he told them that it had been a long time since they had sex with their daughter. Mitsuko's eyes were caught by her son-in-law's big bulge, and she started rubbing it, saying, "I'll help you."