During puberty, Noboru and Akira begin to feel romantic attraction toward their mother's large, shapely buttocks. One day, Noboru is asked by his mother to give her a massage. Overcome by his male instincts, he loses control and bites into her plump rear. Meanwhile, Akira becomes mesmerized while watching his mother's voluptuous backside covered in bubbles in the bath, losing all self-restraint. Both sons are driven by the same uncontrollable urges.