Damn, great vibes! The art is really disturbing, crazy high attention to detail. Storyline shows much promise, I would've loved to see where it goes next.
I had some frustration figuring out the layout of the game map (there are 2 floors... but going right teleports you to the 2nd floor, and yet there is also a window from 1st floor to the 2nd floor - how does that work?) and the rules by which the demon behaves (he can spot me from the first floor when I'm on the second floor... does he do that through the window when he stands next to it?), and died a lot because I couldn't find the 2 hiding spots on the map for a while (thanks for the cutscene skip function btw). But I think it was worth it in the end.
Voiceover was awesome. It was also surprising to see multiple languages and voiceovers (что редко встречается в джемных играх), and of the high quality too!
I thought the game bugged out because it returned to the main menu after the mirror scene, yet the description & narrative mentioned multiple demons, had to source dive to double check it's just Beelzebub. I'd suggest putting an "end of demo version" screen, or making it more visible in game description.
Overall, I think you did an outstanding job here, team, this is certainly a unique entry!