Takashi Natsume, orphaned and passed between relatives who found his ability to see youkai unsettling, inherits the Book of Friends from his late grandmother Reiko. The book holds the true names of spirits she defeated and bound to her will, and now those spirits seek out Natsume to reclaim them. Accompanied by Madara — a powerful spirit who takes the form of a lucky-cat figurine and goes by Nyanko-sensei — Natsume sets about returning the names one by one.