Luke watches the exchange with growing amusement, the flush of the girl's cheeks and the way Derek take advantage of her obvious interest. It would remind him a little of Jace, but there's a distinct lack of ego in the entire exchange. Jace carries with him the inevitable arrogance of the Shadowhunters and there's not even the slightest flicker of that in Derek.

"Either get her number, Romeo, or let's move on," he says finally, when it's become clear Derek has all but forgotten he's there at all. He doesn't mind moving on alone if he has to, but he thinks Derek's cat might be less annoyed if they're both there to take it back to Luke's place.