That still leaves us with the rest of the Heaven's to be suspicious over. Or potentially somebody from the Near Shore...

Suijin said it was somebody outside of Japan, so that's... narrowing it down a bit, but not by much. Japan is a very small percentage of the general population.

The outside is a perfect copy of the apartment I lived in at home, but I think the insides are bigger than I'm used to.

[Or it's just that there isn't as much stuff cluttering the rooms.]