"Really interesting, so being in this world you had no knowledge of anything outside." Senku laughed a little at his conclusion. "That's not so weird. My best friend is kind of a lot like you." He paused. "But I think you're smarter than he is. Taiju is great, but he's a physical guy, not much of a bookworm guy."

He hummed. "A parallel world is when there's two worlds, like say yours and mine, that are running side by side, never to meet. But you crossed into the other world, which is even more interesting. When it comes to sci-fi, a lot of them are just other versions of the same world, like what you're talking about as opposed to yours and mine as an example."

"In fiction, someone always crosses over, and while the theory of how those worlds could exist, getting from one to the other seems impossible or unlikely. It's a math thing." Senku paused. "Or physics. There's no proof, it's all theoretical."