Nana is a character from the games Crackle Cradle and Blank Blood...and maybe Fox Tales.
Apparently, she seems to be the most popular character out of the other two, Ryoko and Yuki ...or three, if you count that Foxgirl from Fox Tales.

-EDIT- (As if anyone cares) I had to edit/re-upload due to some glitch that caused the media to show my Mad mod skin, and not this one.
Also, I polished the skin a little more while I was at it.