After divorcing her abusive husband, Chisato lives a peaceful life with her son. However, her sexual frustration grows and she finds relief in masturbating every night. One day, Chisato is threatened by her landlord, Kurihara, and is forced to have sex with him. Although she is reluctant, her body aches from the long absence of sex. That night, Chisato accidentally sees her son's erect penis and becomes aroused again...