First off nice drawings!
Okay just 2 things I'd like to say about the last 2 drawings.
1) The colored one (Blue haired guy Haku) His ear is too far down! It should be in line with his eyes. Imagine if he were to put on a pair of glasses. Do you see how funny that would look? Easy fix. Next time draw his ear higher. In line with his eyes. Just use your own face for reference if nobody is around to look at.
2) I believe that the girl drawing would look a lot more cuter, if her shoulders were not so broad (meaning wide, square). Broad shoulders usually shows masculinity, not femininity. Next time try to not make her shoulders look too wide or maybe it's her head that's kinda too small? hmm, I'm not sure now
lol
Anyways, keep practicing your art and thanks for sharing!