When Yuki was born, his father had disappeared. Despite the opposition of those around her, Hotaru gave birth alone, raised Yuki, and even entered college. Partly because they were close in age, the two were more like friends than parent and child. One day, Yuki took advantage of her summer vacation to invite Hotaru to a hot spring trip. Contrary to Hotaru who was looking forward to her trip, Yuki invited her to travel because she wanted to tell Hotaru when she became an adult...