The story is of a girl named Haru, a quiet, shy and unassuming high school student who has a suppressed ability to talk with cats. One day, she saves a darkly-colored, odd-eyed cat from being hit by a truck on a busy road. The cat is Lune, Prince of the Cat Kingdom. As thanks, the cats give Haru gifts of catnip and mice, and she is offered the Prince's hand in marriage. Her mixed reply is taken as a yes.
Wanting none of this, Haru hears a kind, female voice, which tells her to seek the Cat Bureau. Haru meets Muta, a large white cat the voice told her to seek for directions, who leads her there to meet the Baron (the same Baron from Whisper of the Heart), who is a cat figurine given life by the work of his artist, and Toto, a stone raven who comes to life much like the Baron. Soon after meeting them, Haru and Muta are forcefully taken to the Cat Kingdom, leaving Toto and the Baron in the human world to follow the group from the air. The Baron and his crow friend find the entrance to the Cat Kingdom on Earth: Five lakes forming a cat's paw.