When the Master pulls out a screwdriver, Setsuna pulls away from the wall and starts to walk a bit closer, concerned, but when the Doctor puts a hand up, Setsuna starts to run over. His first instinct is to lurch out and grab for the item, or the Master's arm and keep him from harming the other, not understanding the situation at all.

"Hey, what are you doing?" he shouts while rushing over.