Fireworks - Should We See It from the Side or the Bottom?

Norimichi and Yusuke both have crushes on their classmate Nazuna. A fireworks display is scheduled for the evening, and Yusuke intends to ask Nazuna to join him.

Norimichi and Yusuke are on duty to clean the pool. Nazuna is lying nearby when Yusuke challenges Norimichi to a swimming race. Nazuna overhears them and decides to join. She declares that if she wins, the boys must do whatever she commands. Nazuna finishes first, followed by Yusuke in second place, with Norimichi coming in last. As her prize, Nazuna asks Yusuke to watch the fireworks with her that night, saying she'll wait at his house. Later in the classroom, Norimichi, Yusuke, and their friends debate whether fireworks appear flat or round when viewed from the side. While one boy insists they're round, the others believe they're flat. They make a bet and agree to watch the fireworks together that evening.

After school, Nazuna gives the teacher a letter from her mother stating that Nazuna will transfer schools soon because of her mother's remarriage. Later, Yusuke visits Norimichi at home and reveals that while Nazuna invited him to watch the fireworks, he doesn't plan to go. Noticing Norimichi's injured foot, Yusuke suggests that Norimichi should visit Yusuke's house to get help from his father, then meet Nazuna there to watch the fireworks together instead.

When Norimichi arrives at Yusuke's house, he finds Nazuna already waiting there with her suitcase. After his doctor visit, Norimichi informs Nazuna that Yusuke won't be coming. Nazuna leaves, revealing her plan to run away rather than move with her mother and new stepfather. However, Nazuna's mother discovers this plan and forcibly takes her daughter home. Despite Nazuna crying out for help, Norimichi freezes and does nothing. Overwhelmed with regret, he suddenly throws the marble, desperately wishing he could go back in time.

In an alternative reality, Norimichi beats Yusuke in the race, and Nazuna asks him out instead. When Yusuke visits his house, Norimichi doesn't know how to tell his friend about the date. Norimichi sneaks out with Nazuna, who invites him to elope with her. They are about to board the train when Nazuna's mother discovers her daughter's plan to leave home and forcibly takes her away. Nazuna cries out for help, but Norimichi freezes and does nothing again. After Nazuna is taken away, Norimichi is about to throw the marble again but gets interrupted by his friends. He reluctantly joins them to watch the fireworks and finds it strange that the fireworks appear flat now, which makes him realize he's in an alternative reality. Therefore, he throws the marble toward the fireworks, wishing he could go back in time.

In another alternative reality, Norimichi fights back and boards the train with Nazuna. During the journey, Nazuna shares her dream of becoming a singer in a big city. Their escape is short-lived when Norimichi's friends and Nazuna's mother spot them. They flee the train and hide in a lighthouse. Norimichi throws the marble again, wishing they could remain hidden from everyone.

In another alternative reality, Norimichi knows their friends and families are searching for them, so they hide on the train. This time, they escape without being pursued. The train takes an unexpected route, transporting them to a strange, enclosed world. Nazuna invites Norimichi to swim with her. Meanwhile, a pyrotechnician discovers the marble, revealing it to be a firework shell. When he launches it, the marble transforms into spectacular fireworks. The scattered fragments display their possible futures. Norimichi reaches for the shard showing them kissing in Tokyo, suggesting he embraces this outcome.

The following day, the teacher calls roll. Nazuna's name is no longer on the list, indicating she has transferred to another school, and Norimichi is notably absent from class.