>>280635479>>280635675I thought that the very first scene at the start of the anime was taking place in Denji Heian-Kyo but I was wrong. It seems like it because Takeru is running through a temple area which makes it look like the isekai world, but pic related scene confirms it's the real world. Not a dream and not Denji Heian-Kyo. And Takeru asks "where am I?"
I think it's deliberately misleading.
We were supposed to assume it's either a dream or just a city district Takeru doesn't know, when he is actually lost because he ended up in a different world. My guess is that Takeru was always from Heian, ended up in our world for some reason and some enemies have followed him. Then the gate closes (maybe because Tsukimiya is from our world and using it to go to Heian or some shit) and Takeru is doomed to stay on our planet till his isekai death.
The big question is why both of them have no clear recollection of these pasts. Maybe you slowly forget about the world you came from the longer you hang around in the respective other world.