Nazuna Oikawa, a 14-year-old student in the coastal town of Moshimo, grapples with familial fractures after her father’s disappearance post-divorce. Her mother’s decision to remarry and uproot the family fuels Nazuna’s rebellious streak, driving her to repeatedly flee home in pursuit of autonomy. Though reserved and socially isolated, she attracts admiration from classmates Norimichi Shimada and Yusuke Azumi, who both vie for her affection.

During a school pool-cleaning task, Nazuna orchestrates a race between the boys, staking a date with the winner as incentive. She secretly roots for Norimichi, intending to enlist his aid in escaping town. When Yusuke triumphs, she extends a halfhearted invitation, later confessing her preference for Norimichi after a thwarted escape. Desperation pushes her to wield a mysterious glass marble—discovered near the sea and tied to her father’s death—unlocking its power to rewind time and reshape outcomes.

Nazuna’s impulsive bids for freedom reveal her naivety; she dreams of Tokyo’s nightlife or a singing career but lacks concrete plans. Through fractured timelines, her bond with Norimichi deepens, culminating in a shared dreamlike musical interlude aboard a train, blending yearning for love and liberation. In their final attempt, they enter a glass-domed realm witnessing fragmented futures before the marble shatters.

The following day, both vanish from school, hinting at a successful elopement that echoes her mother’s rebellious past. Their fate—drowned, escaped, or suspended in an alternate reality—lingers unresolved. Nazuna’s journey underscores youthful defiance against instability, her choices a fragile mosaic of agency and rebellion.