When her brother Hiroki disappears after a violent altercation with school bullies, the young Yuriko finds a magical book in his room. The book leads her to another world where she learns that Hiroki has been possessed by a spirit from the Book of Heroes.She visits the magical Nameless Land, where she is told how to save her brother, and is sent back to Earth with a young monk named Sora and the magical book, transformed into a mouse named Azu. Yuriko has to piece together the mystery of Hiroki, and has a library of powerful magical books at her disposal to do so!