ฅ/ᐠ｡ᆽ｡ᐟ \ ~Hello~
There were definitely a lot of strengths in the demo. The setting, lighting, and visuals meshed well together and created a perfect setting. I can't stress the importance of plot enough, so providing a backstory involving unsolved murders and spirits was also a great start. It reeled me in as it basically set the tone for what the game will be about. The biggest complaint I have, however, is the backtracking.
I've noticed other Let's Players comment on it already, so I'm sure by now I'm just regurgitating what's been said before. Backtracking essentially decreased the tension of the game for me. I think it'd be great to replace sections of it with puzzles instead. Puzzles, cutscenes, lore, or basically anything that contributes to actual gameplay or plot. It's important to maintain feelings of dread.
Aside from that, the concepts you've showcased in the demo show great potential. It's just the gameplay itself that may be a little lacking here, so hopefully our suggestions can help you form new ideas.
Overall, the demo needs a bit more polishing, but the concepts are great. With that said, I wish you the best of luck with game development as I think you're definitely on to creating something big with this.