As he lets down his usual mental barriers Lucas is swept up in that very pleasant memory of Max's. It echoes a few of his own kissing Corbin so he doesn't resist at all.

In fact, he just quiets down entirely, eyes drooping to half-lidded with a far away look. Only distantly aware of the other two with him as the conversation carries on. Don't mind him at all, getting some quality HD replays over here.