Beautiful art and excellent mood setting. I enjoyed it tremendously. One thing I'm not sure about is why you have to switch between characters, maybe mapping one wasd and the other arrows might work as well?
Also, you might want to display the hints at level start after restart as well, or implement them as visual aid into the levels themselves. I was stuck for a fairly long time on one level, because I had forgotten the hint. But honestly, those are nitpicks.
Overall a fantastic job, really. Are you going to explore/polish the game in the future?