I loved it! I really like that sort of play on fantasy themes, and the art is really pretty ^^ I also liked the boss battle music, it went really well with the game.
I had a bit of a bug for the boss battle as in I was alone (so I got killed) but when I respawned my monster friends were with me so I still had the appropriate ending. Also I know it wasn't the point but the fact I had to respawned before I managed to win set kind of an interesting parallel with the ending (heart-wrenching ending, I might say, good job) and now I have this little headcanon that both of them will respawn again and again in some sort of purgatory manner and maybe at some point they get tired of it and become friend, right?
Anyway xD I really enjoyed playing this and the actual story was quite nice! And so were the characters dialog and interactions.