Sayoko Machimura is a kind and gentle housewife whose marriage has been sexless for years, leaving her inner desires growing stronger each day. During the quiet hours when her son is at school, she has developed the habit of masturbating alone. One day, her son's classmate accidentally discovers her in the act and seizes the opportunity to blackmail her. Once the other classmates learn of her secret, they gradually turn her into their sex slave, escalating their demands. As their desires spiral out of control, they push her into unimaginable acts right before her son's eyes.