Takashi Natsume, a young man with the ability to perceive youkai, is followed by Natsume Yuujinchou San. In the "Book of Friends," Natsume and his bodyguard Madara, also known by the alias Nyanko-sensei, continue to work to free the youkai from their obligations. Natsume accepts his capacity to perceive youkai and ceases viewing it as a curse. He begins to love both his human and youkai companions more as he spends more time with them, and he comes to the conclusion that he need not choose between the spirit and human worlds in order to be happy.