Yamamoto, a man who comes to visit Kanako, is the stepfather of her son Kiyoshi, and this sparks intense jealousy in the boy. Kanako notices his distress, her maternal instincts awakened, and she begins to draw closer to the lonely Kiyoshi. Soon, their love takes a twisted turn—openly, in broad daylight, the mother and son cross the line, beginning a sexual relationship. With no way to turn back, their bond spirals into a tragic tale of forbidden love.