High school student Natsume could have had an ordinary high school life, but he could see monsters and was troubled by it. Many times, he was almost killed by monsters. By chance, Natsume met the cat god. The cat god told him that Natsume's grandmother Reiko had a "Friends' Book" which recorded the names of all the monsters defeated by Reiko. After Reiko died, the monsters entangled Natsume to get their names back. Only by returning the monsters' names to them can Natsume resume a peaceful life. In order to return to a peaceful life, Natsume and the cat god took the "Friends' Book" and started a monster-hunting journey, and a series of touching stories about monsters were brought out.