[ no it's absolutely not the hair. Just the name, really. And when Takizawa mentions Japan, Kaneki figures the world he comes from is at least "Earth". Might not be the same Earth - Kaneki is not about to ask if cannibalistic humanoids called Ghouls exist there - but it's at least Earth and it has a Japan. That is close enough for Kaneki ]

Well, I was wondering if we are all from different worlds, or if we all come from the same "Earth". I mean- [ kaneki looks up at the sky for a moment ] I'm guessing it's the first, but there should be a reason why we are all here, no?

[ are only humans arriving here? No, Kaneki isn't exactly a human is he? So that's not the best theory. Maybe they are all from an "Earth"? ]