Neko no Ongaeshi

Haru Yoshioka saves a cat from being hit by a truck and later discovers that he is Prince Lune of the Cat Kingdom. The Cat King decides the proper reward is to shower her with thoroughly unsuitable feline gifts and then offer her marriage to his son. A small misunderstanding convinces the cats that Haru has accepted, and she is carried into their kingdom, where even her body begins slowly changing into that of a cat. Her best hope is the Cat Bureau and Baron Humbert von Gikkingen, the elegant cat who follows to rescue her. Surrounded by feasts, chases, and bizarre royal customs, Haru realizes that returning home depends on something simpler than magic: holding on to who she is instead of letting others decide her life for her.