A married couple visits the wife's parents' home. That night, Yuu, the mother-in-law, brings shampoo to her son-in-law while he's bathing and offers to wash his back. Noticing his obvious erection, she gently begins stroking his crotch. Unable to hold back, he ejaculates, and she tells him to keep it a secret from her daughter, sealing it with a tender kiss. But his arousal doesn't end there, and their forbidden relationship deepens. As their affair grows more intense, he even cums on her sleeping face at night●. Eventually, the daughter finds out. Six months later, when he learns his wife is going on a trip with friends, the first thing he thinks of is his stepmother. Before he realizes it, he's sent her an email. A few hours after his wife leaves, the doorbell rings—and there she stands, his stepmother, shy yet clearly happy to see him…