Yukako's son Takashi was a ronin. One night, when Yukako brings dinner to Takashi's room while she's studying, she finds a naughty book under her reference books. It was also a mature woman's naughty book with a woman of the same age as Yukako. Yukako tells Takashi that he shouldn't be interested in a mature woman any more, so she gets naked and shows Takashi masturbation, and makes Takashi masturbate.
