Takashi Natsume has never fit in because of his unusual ability to see strange creatures known as youkai. He was isolated and lonely as he was moved from foster home to foster home. He's come to accept that no one will ever believe him and has cut himself off from his current caregivers and classmates. When Natsume inadvertently breaks an intangible barrier, he liberates Madara, a powerful spirit in the form of a lucky cat. Madara notices that Natsume resembles his late grandmother Reiko Natsume, an outcast girl who became famous throughout the youkai world for creating the Book of Friends. Natsume now possesses it, as well as the ability to summon the written names of the youkai Reiko defeated.