The narrator tells us that he's worried about his friend, Hinana, who's still stuck in her childhood. He's going to go to the gym with her, and he wants to know why they're taking their clothes off so they can do it. He tells us about the first time he met her, when they were both in first grade. Hinana was a ditzy, happy girl, and the narrator was floored when he heard her play the piano in a competition. Her mom was so proud of her daughter that she even locked her in the closet when she calmed down. The narrator decides that he needs to stop being a spoiled brat, so he decides to adopt a little sister. He also decides to pursue his dream of becoming a piano player.