He raises his hands to reply, then stops. ... You... aren't really, are you?

There's actual legitimate concern there, given that he hadn't properly interacted with people for... a while. He hadn't ever been the best at reading emotions to begin with; some/too much/no time spent all over time and space doesn't exactly help with that. Sans is chuckling, sure, but he still has to be sure.

Whichever you'd prefer. You don't have to if you don't want to or aren't feeling up to it, but if you'd rather some privacy then... His gaze flickers over to the entrance to the room. Perhaps I'll remember to close the door this time.