He's kind of grinning just before she lands it on him, and for a moment he is mentally blinded by how lovely it is for her to kiss him like that, without mistletoe or jealousy or some other we-can-say-we-didn't-mean-to-in-the-morning. Her lips are soft and she's impulsive sometimes too and he savours it for a beat before he gets one hand on her ribs to steady himself so he can go in on it too. He's going to relish this. It's been too long not to.