Sora and Natsuhiko's parents lived next to each other and were both friends, so Sora and Natsuhiko have known each other for their whole lives. The two attended elementary school together and now attend the same high school. After Natsuhiko was orphaned and moved to live with his grandparents, and since they attended different middle schools, Sora found the time whenever she could to visit him.
During the events of the book, Sora asks Natsuhiko out on a date and confesses to him, after which the two start going out together.
However, when Natsuhiko avoids the prediction that he'll be hit by a train and killed, that misfortune instead befalls Sora. She is pushed from the platform of Kitahiragawa station by a man who she rejects and, with poor timing, is hit by the oncoming high-speed train.
At the end of the novel, Maki-chan travels back in time to this point and saves Sora from being pushed, together with bringing Natsuhiko to her. By doing this, she grants Sora's wish "To be with Natsuhiko" and creates two realities: one where Sora is killed and one where Sora is saved.