Sakuya's motherly expression comes through very well in this piece. I think the variations in skin tone are interesting, too-- you don't see that nearly so often as you'd think.
Very much so, being vampires it seems more than fitting that Remi and Flan would have significantly paler skin tones to that of regular characters who go out during the day like Meiling. I guess the same can be said for Patchy, considering that she doesn't leave the SDM library very often.
When I first saw this pic my first thought was "dang, the artist put in a lot of thought into skin tones"