And Sans looks concerned, as Frisk jumps. The kid looks worried, and he feels his own soul ache with sympathetic worry. But more than that, now that he's getting even a vague sense that something has happened, Sans finds himself starting to feel angry. That's...almost reassuring. Anger is still more familiar than worry, to this iteration of Sans. But if someone really did hurt Frisk, that someone needs to be dealt with.

It's not really subtle, the "kind of" implications, but Sans can be rather creatively dense in very specific ways, where his brother is concerned. Not to mention the fact that even if they're from the same world, Frisk has still lived a completely different life from the human in Sans' time. So for a moment, he looks back at Frisk in blank incomprehension. Of course they don't mean Papyrus. Papyrus would never hurt Frisk, even if he wasn't Papyrus yet. Right?

"there's, uh, there's been a lot of new people around."