I've just finished the demo and I have to say, I'm quite intrigued by the story and characters! The atmosphere is great, the characters are well defined already and I like Sage's chara-design (reminds me of a mixed between Nagito Komaeda and Makoto Naegi from Danganronpa). The dull and cold palette of colors fit the ambience of your story so well! And I like the soft touches of flashy color on the teens' clothes! It makes them even more unique.
I'm impatient to discover more of it! Especially the ghost part of it and also, the romance routes there will be. Good luck for the next step of your work!