Sayuri loves exercise, but neither her husband nor her son will join her, so she usually works out alone. When her son brings home his friend Kosuke, his muscular body makes her horny enough to casually seduce him. His stamina never fades no matter how many times he cums, and he keeps forcing himself on her until morning. Obsessed with her body, he begins visiting several times a day. As she repeatedly satisfies his appetite, countless orgasms push her body beyond its limits.