[Josak had been avoiding Conrad, but seeing him around in that costume is more than Josak can forgo. It's just...too Conrad.
And he knows Conrad wouldn't try to do anything to him here. Josak couldn't care less about the "Hallowed Ween" or whatever people the holiday the party was for, but he did take any chance he could to dress up and enjoy himself.
So he comes up from the side, knowing Conrad would probably have noticed him already.]
You're looking rather...rogue, I would say, dear stranger. One would think you were up to something devious.