My grandfather used to say every now and then: Books possess tremendous power. But what is this power really? The small second-hand bookstore of his grandfather with the huge stacks of books reaching up to the ceiling is the ideal refuge for the introverted teenager Rintaro Natsuki. There he spends happy moments reading whatever he likes. But one night, his grandfather dies in his sleep, leaving Rintaro devastated and alone. It seems that the second-hand bookstore will have to close. Then appears Tiger, a mysterious tabby cat who talks and has a mission: to save books. However, he needs the assistance of a true bibliophile to accomplish it, and so he asks Rintaro to help him.
The strange pair, the boy and the cat, will live through three magical adventures, freeing books from people who imprison them, mistreat them, or betray their spirit. However, the last rescue in their incredible journey, which will bring him face to face with himself, Rintaro will have to undertake alone…