Kahori Harukawa presents an image of perfection as a dedicated piano student. She surfs daily, a practice tied to memories of her late father. Kenji Seki, her neighbor and classmate, secretly watches her morning sessions, his unspoken feelings for her remaining unknown to Kahori.

Serving as class representative, she defies expectations of the role. When transfer student Ryoichi Kyogoku arrives, Kahori feels an instant pull towards him, especially after hearing him play "Claire de Lune" on the piano. This connection sparks a star-crossed romance, complicated by Kyogoku's secret identity as a time traveler from humanity's future lunar colony.

Lacking psychic abilities, Kahori stays outside Kyogoku's recruitment efforts. Her involvement in the central conflict stems purely from romantic tensions: Kenji's unresolved affection for her and her own deepening feelings for Kyogoku. This dynamic fuels jealousy, straining her friendship with Natsuki Suzuura, Kenji's childhood friend.

She witnesses the final confrontation involving Kyogoku and Kenji. Following the resolution, she loses her memories of the supernatural events and Kyogoku's existence, like most others. However, after the main events and a post-credits scene, her memories are restored upon Kenji's return to the present timeline.