A film depicting the moment when the prim and proper married woman, Itsuko, experiences anal orgasm for the first time. Under the skilled hands of an esthetician, her mind and body are gradually liberated, drawn into forbidden pleasure. Her anus is stretched by fingers and a vibrator, then overwhelmed by the intense sensation of a large cock thrusting deep inside. Despite her refined appearance, she loses control completely, exposing her lewd, desperate state. The erotic progression, moment by moment, is the film's greatest allure.