Yusuke cannot take his eyes off the sensual body of his mother’s best friend, Mami, after she unexpectedly arrives at his home. His clumsy attempts to attract her attention go nowhere, so he plans to masturbate with her freshly removed underwear while she bathes. Mami catches him when she comes out, but instead of scolding him, she links arms with him and asks whether he wanted her that badly, turning an ordinary day into an unforgettable memory.