Akaneko no Akuma

Yamane Akaneko and Tsujishima encounter a supernatural secret while in their nearly empty school library. A red cat, revealed to be a demon, takes control of Tsujishima and asks for their help in protecting the library's books. These books contain self-consistent stories that exist as real worlds. They are threatened by "bookworms," cat-like creatures that consume words and alter the stories, eventually destroying their realities. Together, Yamane, Tsujishima, and the possessed cat travel into the worlds of various books to locate and capture the bookworms before they cause irreversible damage.