Koma is a white cat with distinctive black circles atop her head and pink ears. In the spin-off anime "Uchi Tama!? ~Uchi no Tama Shirimasen ka?~", she appears as a human with styled white hair, darker hair sections above her eyes, pink inner ears, and violet eyes, wearing mixed black and white clothing.

As a kitten, she is still learning about being a cat and about life. Her owners run a bathhouse, making her unafraid of water. She enjoys chasing things and spends much of her free time with Momo. Koma admires Tora for his adventurous spirit, though they often tease each other. She also likes spending time with Nora, dragging him around to hang out with the other animals of Third Street. Her designated job is to assist people at her owners' bathhouse.

In the episode "Have You Seen My Tama?", Koma joins Beh and Tora in watching their owners put up missing posters after Tama disappears. She goes to the Tulip Cafe to inform Momo, and they search together. They find a house with a dog bowl full of cake, and Koma eats the food without concern for ownership. Momo reluctantly joins, but both flee when confronted by an angry male dog. Later, Koma is in the park with the other Third Street animals, expressing worry about Tama until Tama and Pochi return.