Staying over at his friend's house, Ueda becomes captivated by the beauty of his friend's mother, Taiichika, finding himself increasingly obsessed with spending time with her rather than just hanging out with his friend. One night, Ueda accidentally witnesses Taiichika masturbating while talking on the phone with her secret lover. Trembling with shame, she pleads with him to keep it a secret, but Ueda, overwhelmed by desire, takes advantage of the situation and blackmails her—unless she wants her affair exposed. Days later, their twisted relationship takes a new turn.