Masami was visiting her daughter's couple's house to arbitrate a fight. I want my daughter to be happy. And hopefully I'll see my first grandson. Although it was an act from pure feelings, the cause of the disagreement was that his son-in-law secretly lusted for Masami. That night, Masami, who was to stay at the daughter's couple's house, relaxed, took a bath, and went to bed in light clothes. Masami was unaware that such casual behavior had stimulated the forbidden desires of her son-in-law.