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. However, 7 years before the novel's current events Natsuhiko's parents were killed in a hit and run by the famous actor Itsuki Shindou which caused Natsuhiko and his younger sister Momiji to be taken in by their grandparents.
At the beginning of the novel, Itsuki Shindou plans to release a compilation of his prison memoirs. The threat of Natsuhiko's peaceful life being destroyed again by public interest into Itsuki Shindou's case, the possibility of a retrial and people like Jirou Asai pressuring him to talk about the case causes him to hold the strong wish - to live in peace. Maki grants this in the form of a future predicting card.
This helps restore the peace back into Natsuhiko's life. During this period he and Sora begin dating and the Itsuki Shindou situation seems to bring itself to an end. However, when the card predicts that he will be hit by a train and killed, and Sora is instead killed as a price for avoiding that misfortune, Natsuhiko slowly begins to lose the peace in his life again.
Natsuhiko reveals that he is indirectly responsible for Sora's death to Akito, unknowing that Akito's wish for "Appropriateness" is being granted by Ruma. After which, Akito orders Ruma to kill him in retribution for Sora's death, who Akito secretly loved. At first Ruma is unable to surpass the power of Maki's card, but succeeds in killing him when Natsuhiko sacrifices himself to save Maki, slicing his stomach open with her scythe.
After Natsuhiko is killed, Maki travels back in time to the point before Sora is killed to grant her wish - to be together with Natsuhiko. In this alternate reality, Natsuhiko's card tells him to go to the train station where Sora is, and then disappears.