While testing your demo, enjoying your beautiful art and your original concept ('cause there are and I enjoyed it :) ), I encoutered some problems. Indeed, playing on a keyboard alone, I had difficulties controlling both the character and the lightfairy and had to quit when those skills were the most required (I don't know if it's me who is terrible, or if other tester had the same problem ^^" ).
Apparently on gamepad (or even in coop) this problem is not a real one, but maybe a message inquiring the player to use a gamepad could help :)
Also, but this may be only my tastes, or it's intentional, I find the little girl quite disturbing ^^"
Except those "negative" comments, it's a wonderful game and I hope you'll be able to make it a full game :)