Shy and gentle son Ryota evokes feelings in his stepmother Satomi that surpass those of a mother. One day, Ryota invites his friend Daisuke to their home. Satomi is delighted but is caught by Daisuke masturbating while calling out Ryota's name in the living room, and is blackmailed into submitting to him. Afterward, Satomi is also at Daisuke's beck and call, becoming his sexual plaything.
