Neko-Musume (GeGeGe no Kitaro)

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Neko Musume (猫娘, Cat Girl) is a young youkai with the appearance of a regular girl, however she has the ability to call out her cat-like features.
A normally-quiet yōkai girl, who transforms into a frightening cat monster with fangs and feline eyes when she is angry or hungry for fish. Predictably, she does not get along well with Nezumi-Otoko. She harbors a crush on Kitarō, who sees her only as a friend. In recent iterations (possibly due to the recent anime phenomenon of fanservice), she is very fond of human fashion and is seen in different outfits and uniforms.
Information from: GeGeGe no Kitaro Wikia