Nyanko-sensei, also known as Madara, is one of the main characters of the anime series Natsume Yujin-cho. He is a powerful youkai beast but usually takes the form of a maneki-neko. Throughout the series, Nyanko-sensei acts as Natsume?s bodyguard under the contract that when Natsume dies, Nyanko-sensei will inherit the Book of Friends.