Since childhood, mother Masako has showered her son Yuki with abnormally deep affection. However, as Yuki gradually grows up, one day he suddenly begins showing intense interest in his mother's back and buttocks. Surprised by his reaction, Masako slowly starts deliberately exposing her body. As a result, Yuki's male instincts begin to awaken, and his feelings toward his mother start developing into a new, forbidden desire.