Karada Iokawa is looking forward to starting junior high school. She's a jovial and dependable girl, but she hates being treated like a child. Her parents pass away and her older brother Hiro comes back from overseas to care for her with his ex-girlfriend, Shouko Nogami. Shouko is a calm and sometimes stubborn young woman who moved to Japan to confront Hiro about their break-up. The stress between the two girls intensifies when Shouko accuses Karada of being childish. In a later scene, Karada prays at a sacred shrine to transform into an adult. She doesn't know that a wishing stone at the shrine grants her wish, causing her to age rapidly. Shouko, who is nearby, turns into a child again. With their roles flipped, Shouko and Karada must rebuild their relationship and overcome their struggles.