Interesting take of a game!
A few issues I encountered:
The text from the book talking about the Swedish witch trials was WAAAY too fast. I consider myself a fast reader and I wasn't able to catch all of the information given to me in that text. If possible, either slow it down a tad, or make it possible for the player to either progress the text forward with a click or at least to be able to read the book again so that they can get the information needed. I feel like I was partially robbed of vital clues for the following puzzle (and a very interesting history lesson) with all of that.
I had the camera shift to a wonky angle on me a couple of times and it took me a bit to fix it so that I could see properly again. Not a major issue, but something I figured I should point out.
Speaking of minor issues, Rei does glide a bit with her walk cycle from time to time and there also still seems to be minor lighting issues at certain points.
Also, I had to CTRL+ALT+DEL in order to get out of the game once the demo was finished. I suggest putting in an escape prompt for that so that players don't have to constantly pull up the task manager in order to close the game.
Otherwise, I do like the game in concept. I think it will work very well as an exploring/puzzle-solving spooky adventure. The only thing that I think would help improve that aspect on it is to instill more of an atmosphere for the game. Certain things just happen a little too abruptly and become more jarring than anything. Also, would have LOVED to see some sort of "black substance" in the room where I was first puzzle-solving when the ghost showed up as mentioned to give it a bit more of a sense of urgency.
I understand that the dev team was under massive time constraints for this, so please don't take my criticisms too harshly. For a demo, it is solid. The controls seem to be intuitive (played this on a Windows PC) and everything looks aesthetically pleasing. I do think this game has a lot of potential and look forward to seeing what you all do with it moving forward!