Yugako's son, Takashi, was a student preparing for his entrance exams. One night, Yugako brought him some midnight snacks while he was studying and found a pornographic book under his reference books. It was a pornographic book with pictures of mature women of the same age as Yugako. Yugako told Takashi that she didn't want him to be interested in mature women any more, so she got naked and showed him how she masturbated, and made him masturbate too.