After his older brother's marriage, the younger brother becomes infatuated with his new sister-in-law, Reiko. A woman of experience, Reiko immediately recognizes the playful nature of her brother-in-law, who begins seducing her. Yielding to his advances, she grows wet with desire. Taking advantage of her husband's absence, they repeatedly indulge in their forbidden affair, their passion unrelenting. The illicit desire between these two siblings-in-law continues endlessly.