Within a country akin to a tower, rabbits live in towns on the upper floors 1 to 13, and the oppressed wolves live in the lower stratum. The lower the floor, the worse the living conditions and security get. To move up, a key is needed as proof of passage, but moving down is unrestricted. In this kind of country, a rabbit named Bell has the daily task of capturing wolves, and will savagely kill any that enter her domain. Despite all this, a wolf appears by her side–!?