Kyoko Takashima, 32 years old, is married and has a family, but Kyoko is not getting enough exercise, so one day she decides to go on a diet... Her stepmother, wearing a tight-fitting leotard, arouses her son, who begins to fantasize about her. He starts peeking into his parents' bedroom and his mother's bath. The stepson's young crotch is filled with sexual desire, and one day he can no longer be controlled by fantasies and masturbation, and he turns to his stepmother...