小さい頃から妖怪を見ることができた少年・夏目貴志は、祖母レイコの遺産「友人帳」を受け継ぎ、
自称用心棒のニャンコ先生と共に、そこに名を縛られた妖怪たちに名を返す日々を送る。
妖と、そこに関わる人との触れ合いを通して、自分の進むべき道を模索し始めた夏目は、想いを共有できる友人たちにも助けられながら、大切な日々を守るすべを見つけていこうとする。
As a young child, Takashi Natsume believed his ability to see youkai to be nothing but a curse. Now a high school student, Natsume has managed to heal from his old wounds and form unbreakable bonds with humans and youkai alike. Natsume's newfound friendships—including the one with his spirit bodyguard Madara, nicknamed "Nyanko-sensei"—are often interlaced with his duty to return the names of the spirits written inside the Book of Friends, his late grandmother Reiko's keepsake. While more remarkable youkai reach out to him, Natsume discovers that he still has much to learn about the world that surrounds him.