Goba, who is set to compete in the prefectural swimming tournament. The venue happened to be near his grandfather's house, so he stayed there during the competition. His grandfather, whom he hadn't seen in a while, was kind and, since it was Goba's birthday the day before the tournament, even prepared a cake for him. That night, Goba collapsed into sleep due to sudden drowsiness. When she woke up, she found herself tied up in the storeroom. Confused, she saw her grandfather's figure with a strange smile appear before her...
