The cat-girl is the unnamed main protagonist of The Valley Rule. She is trying to collect each of the four keys to open the door to the surface.
The cat-girl appears as a small girl with a white dress, white skin, and crimson hair/fur. She has humanoid arms and legs and feline ears, as she is a hybrid of a cat and a girl.
The cat-girl can obtain abilities to help her collect the necessary keys. If she comes in contact with water, she instantly dies and is re-spawned at the last save point. Her goal in the game is to make it to the surface, which a door presumably leads to. After the door is entered it is made uncertain if she makes it to the surface or not, as this is where the game ends.