If you knew you didn't have long to live, who would you tell? What would you say? And how would you deliver the message?

The Keeper of the Camphor Tree starts with Reito Naoi, a man in his early 20s, being unjustly fired from his job. Enraged and fueled by feelings of revenge, he tries to steal a valuable device from his workplace, but things don't go to plan, and he ends up arrested.

In jail, Reito is paid an unexpected visit by a lawyer who offers to arrange for his release, if he complies with the wishes of the lawyer's client. Seeing no alternative, Reito accepts and soon discovers that the lawyer's client is his aunt. When Reito tells her that he has no plans for the future, she gives him an order: "What I want you to do is to guard a camphor tree." And thus begins Reito's custodianship of a camphor tree standing on the grounds of a shrine—a camphor tree with a mysterious legend associated with it.