Natsume Takashi has the ability to see spirits, which he has long kept secret. However, once he inherits a strange book that belonged to his deceased grandmother, Reiko, he discovers the reason why spirits surround him.
Natsume discovers that the heirloom "Book of Friends" that his grandmother, Reiko, gave him possesses the names of the spirits she defeated and bound to her will. Assisted by a cat whom Natsume addresses as Nyanko-Sensei (lit. Master Little Meow), Natsume aims to return all of the names to their rightful owners.