As her mother Junko is eating snacks and reading a magazine in the living room, her son Daisuke asks her, "Mom, haven't you gained weight recently?" She hadn't noticed it, but when she weighed herself in the dressing room, she was clearly fat. What's more, her breasts had gotten bigger. Junko then consulted Daisuke, saying, "If you gain weight, your breasts will get bigger too..." and they decided to start training together, but... Since then, Daisuke has been obsessed with Junko's breasts...