Mother Junko was in the living room, reading a magazine while eating sweet snacks. Watching her was her son Daisuke, who remarked, "Mom, have you gained weight recently?" Taken aback by his comment, Junko hadn't realized it herself—until she stepped on the scale in the changing room and noticed her body had clearly changed. Her bust size had grown significantly too. Realizing this, she said to Daisuke, "So when I gain weight, my breasts get bigger..." and consulted with him about it, deciding to start working out together. From that point on, Daisuke became increasingly aware of his mother's breasts, finding his attention drawn to them more and more in their daily lives...