"And what, you would just leave me alone if I did?" If Sora sounds skeptical, that's because he is. It's not that he's worried about what Xehanort might be up to - there wasn't really much that he could get up to here, as far as Sora could tell, though he'd have to keep an eye out for signs of trouble. It's just that Sora can't really imagine it being that easy to ignore each other.