It's a fair assumption, one that he's been making, too! Names, speech patterns, food, all the right boxes are checked for 'Japan', or if not there specifically, somewhere that would be comparable enough.

"I'm familiar with Japan," no need to try and explain that one to him! "It does feel like a number of us are from there, or... somewhere that's basically the same."

Ah, there we go, this is already feeling a lot less tense than before. It's not enough to shake off that heavy atmosphere, (and, surprise, it won't be,) but it isn't a completely uncomfortable topic yet, which is a relief.