I already expressed my love for this one in Skype, but once again, it's these kinds of artworks that I really enjoy seeing from you ;v; (not that I don't enjoy the more detailed!). There's just something about the more simplistic pieces where the impact relies on the subject and the little coloring; where you're not mindblown by the beautiful coloring and highlighting and shades. I find it really neat how, despite the strong colors of red and black and white and their contrast, this artwork still looks very light thanks to Rei's pose and the flow of the scarf and hair. Sharp yet carefree? Her gentle expression adds to this unique contrast.
Furthermore, so few colors are used, yet the way you've incorporated them into this artwork doesn't feel overwhelming. More kudos for that.