Son begins living alone in the city. Residing in a small urban studio apartment, he learns his parents will be visiting from the countryside. His stepmother, Yui, concerned about her son's lifestyle, feels slightly troubled by the messiness of his room. That night, the father suddenly has to return home, leaving Yui to stay overnight at the apartment. Lying side by side on futons in the tiny six-tatami room, the stepmother's presence becomes too much for her son to bear—his cock can't help but grow excited. Torn between the stepmother's tenderness and the intimate atmosphere of the room, emotions begin to stir, leading to an irresistible, forbidden connection.