Living with his brother and his wife, Yukichi accidentally catches a glimpse of his sister-in-law changing clothes. In that instant, the image of his brother's wife, Chisato—her voluptuous curves and soft, big tits—burns into his mind. Captivated by her beauty, forbidden desires begin to stir within him. Unable to control himself, he steals her underwear and indulges in masturbation, only to be caught in the act by Chisato herself. But what does she truly think about his actions?