1. After looking at the picture for quite a while, I found that the "Hair" shape looked somewhat unbalanced, though it is hard to see, it is just a small and minor error.
2. Her nose looked somewhat "dislocated" maybe another shaped nose or relocate it..? I'm not sure... But again, this is a small and minor mistake that doesn't cost much.. (Check the images below for some examples if you want)
3. Unnatural hair shape: The small slash from the left-middle to right looked "unnatural..." (Somewhat..) Maybe remove it..? But then the hair shape will be more unnatural.. and... (the right part of his hair is larger than his head..?)
4. Fix the blushing please!!! It looks weird for a smirking face...
Though I'll NEVER draw better than you can or as good as your picture, I hope these tips can improve your drawing.