[He's blushing now, eyes drifting downward.]

Are they? That is an...odd custom, I suppose.

[It's pretty obvious that he's not sure how to proceed, but then he takes a breath and steels himself once again.]

Well, we are under the mistletoe, and you have kissed me, so I suppose that I should kiss you as well?

[Gonna do this right, darnit! He will master the local customs!]