Yasaki Yui is an ordinary housewife living with her daughter, son-in-law, and husband. She leads a peaceful life until one day, her underwear suddenly goes missing—an eerie incident that leaves her disturbed. "Who would want the underwear of an older woman like me?" she wonders, growing suspicious. The culprit, however, is her son-in-law, who has long been attracted to her obscenely large breasts and has been struggling with pent-up desire. Unable to resist any longer, he finally makes his move and assaults her. Though Yui resists at first, her emotions begin to waver, and she soon finds herself helplessly toyed with by her son-in-law like a plaything.