Just going off the other pieces in the same set on pixiv, I believe it may be Cirno and Mystia again. I see black wings at the reddish-haired girl's back (per the design in post #1270187) and what looks to be a ribbon in the blue-haired girl's hair. All of the characters that appear in the set seem to be tagged on pixiv and Mystia and Cirno are among those names.
I'll go ahead and tag them here unless there are any objections!
