Nora, Princess, and Stray Cat

Nora, Princess, and Stray Cat (2017) is a animation, drama with 1 season, rated 4.8/10.

Nora Handa is a high school boy who meets a girl named Patricia in a park who claims to be a princess of the underworld. Patricia and Nora accidentally kiss, and this act turns Nora into a black cat. Patricia takes Nora to her home, and a few days later Nora turns back into a human. However, Nora keeps turning into a cat and back into a human.