Norimichi Shimada is a teenage student living in the coastal town of Moshimo. His ordinary life entangles with the supernatural when he encounters a mysterious glass marble found by his classmate, Nazuna Oikawa. This object grants him the power to rewind time, which he uses primarily to try preventing Nazuna from moving away with her family.

He possesses dark brown hair and brown eyes, typical of a Japanese middle-school student. Initially reserved and hesitant, especially around the Nazuna he admires, he struggles to approach her directly. When Nazuna challenges Norimichi and his friend Yusuke Azumi to a swimming race—promising to invite the winner to the summer festival—Norimichi loses in the original timeline. Witnessing Yusuke abandon Nazuna and her distress during a confrontation with her mother, Norimichi uses the marble to rewind time. In this altered reality, he wins the race and accepts Nazuna’s invitation.

Driven by a growing determination to protect Nazuna, Norimichi repeatedly resets events, attempting to evade her family and secure their escape. These actions strain his friendship with Yusuke, who grows hostile as Norimichi prioritizes Nazuna over their peers. The time resets trigger surreal distortions: fireworks appear flat, the town becomes encased in a glass-like dome. Amidst these fractures in reality, Norimichi's focus stays fixed on staying with Nazuna, culminating in a final timeline where they share an underwater kiss as reality disintegrates.

The story concludes ambiguously with Norimichi absent from school the next day, suggesting he either succeeded in leaving with Nazuna or entered another reality entirely. His journey transitions from hesitation to proactive defiance against external pressures, his motivations centered exclusively on aiding Nazuna. The marble's power facilitates his emotional journey, underscoring his willingness to reshape the world for their connection despite escalating chaos.