[Souji knows Ian's body language well enough to know exactly what he's doing alongside those movements. The talking-back tone gets an exasperated look from Souji and a tilt of his head. It would have also gotten a smartass response of its own, if Souji hadn't actually been caught off guard by the attack. Well, it was what he had asked for, and he knows he was stupid to have not expected Ian to succeed in doing such things.
Still, it's good. It helps keep him on his toes when Ian doesn't go easy on him.
While the distraction shot works to get his attention, it does little to distract him, purely because he knows Ian's tactics well enough to know Ian would never purposefully miss. As soon as the shot is fired, Souji turns his sword over again, successfully blocking both shots with his sword.
In the next moment, Souji dashes forward, side-stepping Ian at the last moment to roll past and behind him. He doesn't even bother to get back up yet, intending to simply stay on one knee on the ground with his sword pointed up towards Ian's back.]