The Cat Returns (2002)

Haru Yoshioka, a shy high school student with a hidden ability to talk to cats, saves one from being hit by a truck. This cat turns out to be Lune, Prince of the Cat Kingdom. As thanks, Haru receives unwanted gifts and an offer of marriage to the Prince. Haru is taken to the Cat Kingdom, where she starts to transform into a cat. With some unexpected help, she must find her way back to the human world before losing herself entirely.