Natsume's grandmother Reiko can see monsters and has great power. However, she was alienated by the people around her and passed away early, leaving only a friend book. The friend book records the names of monsters that Reiko had defeated, and these monsters must protect the owner of the friend book. After Reiko died, this friend book was left to Natsume. The powerful friend book attracted various monsters to visit, which brought a lot of trouble to Natsume, but also led Natsume to grow up. Natsume pursued the memory of monsters and continued to understand his grandmother Reiko. Due to her extraordinary gift, Reiko was always alone and lonely in the crowd. Natsume, who deeply understood Reiko, wanted to find someone who could understand his heart, and in the process, he also saw the difference between himself and his grandmother. Although life seems to always be filled with the taste of loneliness, it would be very happy if you find someone you want to protect. In such a season from winter to spring, Natsume and his cat teacher brought us a warm current.