The son, who has been watching his stepmother, Kiriko Kinosaki, is so fond of her that one night, he peeks into her having sex with his father and sees his perverted stepmother moaning and climaxing with a vibrator and rotor! He doesn't go to school and continues watching his stepmother, and witnesses her masturbating with a toy while spreading her legs in an M-position. Kiriko, who knows she is being watched, invites her son to have forbidden incestuous sex, saying "I'll treat Ke'ai"! Her nipples become hard as her son licks her, and she climaxes over and over again with her incestuous cock, moaning louder than when she has sex with her husband!