Ten-year-old Natsumi was about to leave for London in pursuit of her parents. As she was waiting for her aunt Izumi, who was supposed to take care of the house during the absence of the family, a time-slipped baby suddenly appeared in front of her with a burst of lightening. In fact, the infant was her future child! Through communication with herself in the future, she decides to raise the baby until it is safely returned to the future world.