I'm starting believe that the Kumon-mi we are experiencing is a form of purgatory/pocket universe and that all the people in it have all died after a certain point in real world. When or how not quite sure. But sure that Maya was the 1st to be placed in and real Sensei was last.
I believe for sure that Sensei is Ami's dad. I think the accident that killed Ami's mom and Sensei's Brother was cause by the truth of Sensei being Ami's dad coming out.
I think Sensei dumped/ghosted Niki when he started with sleeping Ami's mom.
I think Nodoka's mania was given to her to stop her from seeing what beyond the boundary
I think next reset will have Sensei and Maya needing Ayane to go to the roof but also finding out that Makoto, Futaba, Ami, Chicka, if not the entire dorm 1st floor, are also freely wandering around the broken world lost and are needed on the roof to complete the reset.
The Trinity of HOPE, Sekai and the Doppleganger girl makes sense.
Sekai = God of Wires? (because of how she manipulated Makoto and Futaba in threesome scene)
the two silhouette angles, the ones that say: "ssssssss" and "kkkkkkkk", are Sensei's unborn children. (far fetched therory)