The game's concept sparked my interest, and the art matched the mood of the game very well. I thought the puzzles and battles were both interesting (it took me at least two and sometimes three tries to win them, and I liked how you unlock new skills and have different abilities when facing different people). The story was engaging as well, though the dark content may indeed be upsetting to some people. In particular, the flashback sequences were well-done.
Some minor nitpicks: there were some typos throughout the game so I would recommend proofreading if you update the game, and for some reason, the game screen was really small (like 200 pixels or something - was that intentional?), so I had to stretch the window out to play comfortably.
Edit: Fixed typo