[Despite how such a question, and explanation, alike, catches Kazuki's attention almost immediately, he's been debating just whether he wants to respond or not. There's only so much he's told anyone about his home, in part because he isn't sure anyone really needs to know everything else.]
I'm from an island in Japan, which is a country on Earth. [Not that Japan actually exists anymore. The island is man-made. He pauses a little before continuing.] It's known that there's other universes, but humanity has never traveled outside of Earth. As for here, I'm really wondering about what the surface of this world is like.
[Another pause, and maybe a little awkward this time.] . . . My name is Kazuki Makabe. It's nice to meet you, Princess.