An interesting game, for sure. The idea is really fun, the music, albeit a little weird, is fitting, the sound-effects are really pleasing. I would love to see a complete development on this concept. The worst parts of this game are its diminute length and the fact that you can´t actually interact to the game world close to the end.
The length matter is completely understandable on the scenario in which this game was built, but I believe that there should be a way for you to a least tell your monster what to attack (and it having some random change of entering a rage that grows as it grows) or some moveset of sorts to destroy the environment. What I am trying to convey is that this game would be a lot more fascinating if it had somewhat deeper mechanics, instead of being just a walking simulator of sorts.
All in all, I found it fun to watch my monster grow and become increasigly stronger, and I know that, with a bit of development and love, this could become a really enjoyable game and a great take on the “raise and train your monster” idea brought to us by the pokémon series.