In Natsume's Book of Friends, Takashi Natsume has long felt isolated because of his unique ability to see youkai. After being passed between various foster homes, he grew up in loneliness, learning to distance himself from others since he realized they would never accept his experiences. His life changes when he accidentally breaks a spiritual seal, releasing Madara, a powerful spirit who takes the form of a beckoning cat. Madara notices that Natsume strongly resembles his grandmother, Reiko Natsume, who was shunned for creating the Book of Friends—a tome capable of summoning the youkai whose names she had taken. Now holding this book, Natsume has no desire for its power; he simply wants to keep it as a memento of his grandmother and protect it from malicious youkai. He strikes a deal with Madara: once Natsume's life ends, Madara will claim the book, but until then, Madara will serve as Natsume's unofficial guardian, known as Nyanko-sensei. Determined to release the youkai that Reiko trapped, Natsume begins building connections between the human and youkai worlds, strengthening his bonds with both realms.