"Book of Friends" is a Japanese manga series written and illustrated by Yuki Midorikawa. It follows the story of Takashi Natsume, a high school student who can see spirits and youkai. After inheriting a mysterious book from his grandmother, he discovers it contains the names of spirits she had bound to her service. As Takashi navigates his abilities, he decides to return the names to the spirits, seeking to free them from his grandmother's control. The series explores themes of friendship, loneliness, and the connection between humans and the supernatural, making it a heartfelt and engaging read.