[ Kitty's original comment brings a smile to his face but it soon falters, followed by his eyes briefly flickering to her in a clear sign of insecurity. He's already deduced that they've spoken before, but there's a reason why he doesn't listen in on her conversations and although he knows much much better, some habits are hard to break.
Voice edging on tense, he directs his attention to her in an effort to forget Karev even exists. ]