The Cat Returns is actually a semi-sequel to the film Whisper of the Heart. They expand the character Baron Humbert von Gikkingen in a much more notable role than Whisper of the Heart. But even he is not technically the main character of this film.
The main character is a young Japanese school girl named Haru Yoshioka. She’s just minding her own business one day and she sees a bus driver not paying attention. She ends up saving the life of a very lucky cat. Turns out he can talk.
She gets rewarded by the cat’s father. Turns out the cat she saved was a prince, and his father is obviously the king. However, instead of getting simple gifts, the king of the cat world decides to give Haru a much bolder gift.
And that is to give Haru an engagement to the prince. She initially rejects the offer, as it is silly for human girl to marry a male cat. But when she is whisked away to the cat world, she turns half cat. She has to escape the cat kingdom before the end of the day, or she will remain a cat forever.
Overall, The Cat Returns is a rather enjoyable anime film. It’s not the greatest film by Studio Ghibli but definitely one of their better ones. It reminds me much of Spirited Away mixed with Whisper of the Heart.