Overall, a good piece showcasing your strengths
Okay, so this is probably coming a little late, but I have to totally disagree with the previous reviewer. I think this piece is actually very well thought out.
You have a great triangular composition going on here, which moves the viewer's eye very naturally from left to right. The tilt of the neck and the angle of the shoulder and the bend of the knees all create lines which draw attention towards the moon, which really is the focal point of the scene since it's the primary light source, is pretty radiant, and also rather large. Now, all of that might not have been intentional, but that's okay. Some elements of composition can be intuitive, so, you probably have good instincts.
I also think that overall the anatomy of the main figure well done. There are a couple of small problems, but nothing glaring; the hands could use a little work (the right hand doesn't quite look natural as it's holding the lighter and the thumb on the left hand looks just a little big); and, I think based on the angle of her hips and the fact that we're seeing some of her navel, her chest should probably be angled towards us a little more - meaning that we'd see both breasts. Aside from that, she seems pretty well proportioned and you really did a good job of conveying a particular kind of emotional distance in her facial expression.
The coloring and shading is also well done for the most part. If I were to recommend one thing, I would say try and add some darker tones to your shading, maybe adding one or two layers of varying shades of gray (if you're using GIMP or Photoshop, create a new layer, set the layer to multiply and then start shading). I think it would help your figures look a little more solid. I know you're influenced by anime, so, take a look at how some of the figures are shaded and emulate that.
Overall good work.
