The main character of the story moves from the countryside to the city. Soon after arriving, the main character spots a cat about to fall from a rooftop down into the street below. In saving the cat, the main character falls from the roof. Surprisingly, the main character awakes to find that the cat from before has used one of it's nine lives to repay it's debt and return the main character to life! Unfortunately, a cat's life only accounts to a year of life for a human, so the main character must now solve 100 cases in order to regain a full life. A series of strange adventures with animals in human-form ensues.