Kirara

Kirara which everyone in the dub calls Kilala(which I think is kawaii!) is a cat-like demon or spirit who helps Sango. In her small kitten form(see pic) she treated like a pet and she has a larger form that looks a bit like a sabre toothed tiger. She also flies in that form & she's large enough to carry a person on her back. (You can see this in the first season ending credits.) In one epi about the origin of the Shikon jewel, we're given the impression that Kirara has been alive for a long time and her role was to help a female demon slayer. (In that epi she helped a priestess.)