That's a damn good sign, and Ivan has to bite back the urge to make it more intense. He doesn't want to scare the other man into running all the way back to Komarr. No, this is just to get him relaxed. He focuses on that, hands smoothing over his clothes while continuing to kiss, and when he eventually has to break it in order to breathe, he refocuses on kissing the corner of his mouth, along the jaw.

Once he's sure the other man is relaxed and distracted enough not to mind anything else, Ivan focuses on undoing the buttons on his shirt with one hand. If there's one thing he can say about doing things like that and undoing bra clasps with one hand, it's that most people are impressed. And, for some reason, he wants David to be impressed.