"Can't leave?" That doesn't make any sense. None of this makes any sense, but that's the most immediately important thing, so that's what he's focusing on right now.

Roxas' eyebrows now drop into a low, heavy line of consternation. "What are you talking about? Why can't we just use a corridor of darkness to go back?" Which is to say, no, he hasn't tried yet. He hasn't had the chance yet, okay?