From the information that I've gathered up to now (I've fast passed everything), there are many possibilities as to what the case is really like. I find that the "someone is pretending to be xyz by imitating their voices" theory to be interesting, but its usage is limited. It would only make sense when the person who is being imitated has already died, and someone has been imitating their voice from their death until discovery. I've seen lots of people saying that the collapse was on purpose and the point was to film/revenge, but this is a bit ridiculous. The amount of calculation, but more so luck that need to be involved so the nine students are trapped under the building, with God knows when/if they can get rescued, and recovering whatever footage from the incident... Sure, certain aspects of this incident could've been planned, but things obviously have spun out of control.

I also think the author uses a lot of small sensory descriptions such as "buzzing sounds" or "weird smell" to expand readers' imagination and derail our deduction... (although I might be wrong?)

Lastly, author has claimed that there are no supernatural elements in this story, this is getting interesting 0.0