Accompanying his wife on her trip back to her hometown, the husband finds himself irresistibly drawn to his voluptuous mother-in-law, Mari Yonezaki. Since the passing of her husband, she has lived alone, never remarrying, and her solitary life gradually stirs forbidden emotions within him. Left alone together, his suppressed desires grow uncontrollable. While his wife is away, a new relationship begins to blossom between them, soon evolving into an intensely intimate bond. A shocking, deeply passionate encounter awaits, filled with the irresistible allure of a mature woman.