Luka waves the sword slightly left and right, deliberating both how he could break it and if he could break it. He's admiring how gently it cuts the air when Gyre speaks up and brings him back to the issue at hand.

"How did you do that? With your weapon?" Twelve's words implied Luka could break it unarmed, but he can't imagine simply snapping it in half with his bare hands. That was, however, his current plan if Gyre didn't have something more effective in mind.