Hello, I played the demo and thought the plot was pretty interesting.
There were definitely some grammar errors here and there, so I suggest having someone proofread that since english isn't your native language.
I liked how there were some choices to choose from, and I hope they have an impact for the long run inthe full game. The ambient sounds were also a nice touch as they contributed to the atmosphere, but I hope there will at least be some soundtracks thrown every now and then. A lack of music can eventually become boring over time so that's pretty much my biggest suggestion alongside grammar.
Overall, I had fun reading this. Stories with supernatural entities and murder are always quite intriguing to me. Lastly, good luck with game development~!