"But..." Other worlds could not exist; it just wasn't possible. "Yuki claimed we were in Japan, the school Sora comes from is in Japan and is apparently very similar to this one... It doesn't... there can't be..."

"There's no such thing as other worlds..." If there were, well if Charles had managed to enter the world of C and create the Ragonok junction, if there were such things as other inhabitable worlds, then wouldn't he have found them...