Kouta watches his mother cleaning the bathtub. In an ordinary moment, she accidentally slips and falls into the tub. Her clothes are soaked, and her braless breasts become see-through and clearly visible. Kouta is captivated by his mother's sexy appearance, and begins to jerk off as forbidden fantasies surge through his mind. When she notices what he's doing, she confronts him—but instead of scolding him, her expression softens, and an intense, taboo desire begins to stir between them.