It's summer, and Norimichi Shimada and his buddies want to know if fireworks from the side seem round or flat. They devise a strategy to discover the solution at the Moshimo Festival's fireworks show. However, Norimichi is divided when his classmate, Nazuna Oikawa, intends to flee home and invites Norimichi to join her. When their escape attempt fails, a peculiar ball in Nazuna's possession provides them another opportunity to stay together.