When Justin motioned him forward, Draco took the few steps closer and held out his hand formally to Susan. He remembered her from Hogwarts, of course; Draco had made it his personal endeavor to get to know every one of his classmates. His eyes landed on Weasley when the redhead boisterously shouted his own greeting, and Draco couldn't help but wince internally. He was careful not to let anything show physically, though. There were places to be loud, and this clearly wasn't one of them. "Pleased to officially meet your acquaintance, Miss Bones," he greeted Susan formally. "Any friend of Justin's can be considered a friend of mine, as well, if you'll have me."
To most there, that subtle hint would go unnoticed. But if there were ever a Slytherin in that room, for whatever reason, that little sentence would be code for, Justin's mine, so therefore, anyone who is his friend also is mine now. It was just how Draco operated, and he cast Justin a look that clearly tried to help emphasis that point to the former Hufflepuff, just in case his words weren't obvious enough.