Makai Ouji: Devils & Realist character~ ouo
This girl is a female demon (full blooded, fallen angel) that was taken in by Astaroth similar to Dantalion. As such she uses Astaroth's symbol as her own, modded to be without the text. Basically can pass as a male.
Her name is Leandra, which is the female version of the Latin name meaning "lion-man", Leandra's other form is that of a female lion with twisting horns on either side of her head.