I finished the game! I had to use the walkthrough a few times, in my opinion there's a decent number of clarity issues ingame but it was pretty fun nonetheless.
Positives:
I like the voxel art style, it's pretty cute. The sound and general atmosphere is nice. I really liked the letter puzzles, those were really clever and felt good to complete. The ending is pretty interesting.
Negatives:
I think it's ok to not specify which bathroom to go to, but to do so at the start of the game is a bit jarring. When the game tells you to go to a specific locker, I was never able to figure out which one at first (why is the first locker the last one in the back?) I do like the puzzle with the scale, but it wasn't clear to me that it was actually a drawing of a scale so I had to look at the guide. I know one person says what the default password is but I think it could have been more clear that the librarian is using that password.
Even though it's a puzzle game where you have to figure stuff out, I think it's important to make some things more obvious for the player to be on the right track. I don't mean to rag on you or diminish what you've accomplished, I just think it's important to keep this game design stuff in mind. I also don't play these kinds of games too often so it could also partially be a skill issue.