I’m pretty sure this is Nakoruru from Samurai Shodown, but I don’t remember her to have a mask, do you?
Anyway, Nakoruru is living with her grandparent, Sanoku, and younger sister, Rimururu in a place called Ainu Moshiri Kamui Kotan. You could say that the Ainu people are like the Native Americans in the United States; people who are basically very close to nature. Nakoruru’s role in the game is the Defender of Mother Nature, and in some materials, she is refered to as the priestess of the Ainu religion.
I’m seriously wondering what this cosplayer looks like behind her mask… Nice photo still!