Myrokratios said: I'm pretty sure (judging from other pictures by same artist on pixiv) that this is supposed to be the female avatar from Ultima IV, not III.
I'm looking around at similar images on Pixiv, and all I see is the name 'Sister', so it may be an alternate name for the female avatar. Adding it until someone else knows who she really is.
The game is "Ultima Kyoufu no Exodus", the famicom port of the computer game "Ultima III: Exodus." Later the MSX2 port and the NES port were released. The English title of the game is "Ultima: Exodus."