I know I might sound crazy, but I do believe that the tenants of Denji’s current apartment is the surviving hybrids under Makima’s control.

It would explain rules 1: where Asa can’t open any other doors in this building, since Denji might want to keep Asa out of the trouble as much as possible. Kishibe also has to find a place to stash them away too.

Rules 3: You can’t make out with Denji in front of Nayuta. I kinda pondered about this and wonder which woman would ever make out with Denji without some forms of hypnotic spells or a wad of cash, then it kinda dawn on my mind that Reze is still ‘alive’ albeit under Makima’s control at the end of part 1. We’ve seen that Makima’s control can be broken, so it might be possible that once Makima is gone, Reze becomes her former-self and meets with Denji which in turn ignites Nayuta’s possessiveness.

Why would Reze stay in Tatsuki Apartment? I believe that there’s a reason for that. At the end of her arc, Reze seems to make up her mind about escaping together with Denji, so it is possible that she might want to quit her job as Soviet spy. Kishibe knowing this offers her a shelter of sort. She may or may not want to involve with Denji any further, but a peaceful life from her motherland might be an enough incentive for her to stay.

Also, a weird apartment where a hybrid with extreme personality co-exist together can be pretty interesting.

Of course, there’s only four rooms in the building, but there might be a roommate system in place or some might decline the offers and go back to wherever they want.

Hey, this is my theory. Please share you opinion on this.