べっぴん教師　吐息の愛撫 (2004)

Daisuke, who works for a large company, is dating Natsuki, whom he met at a party. When I visit her room, she is absent, and her roommate, an English teacher, Yui, shows up after taking a bath. When he seduces Daisuke, who can't hide his turmoil, he ends up hugging Yui. Daisuke says that he is prepared to break up with Natsuki, but he is kicked out because he doesn't think she's his woman just because he slept once.