A man ends up living with his wife's younger sister, Yukino, and unable to resist her charms, he seeks out Yukino while she is bathing. The man presses his body against his sister-in-law, who is too timid to refuse, in the small bathroom, and the man, getting a taste for Yukino's submissiveness, gropes Yukino further when his wife isn't looking. Eventually, Yukino herself awakens to pleasure and begins to desire the man...