Hmm... would he marry her? Since he didn't seem to have any intention to kill her too that night, so maybe he was just going to marry her and take the throne. She would be next in line so that means he would have killed her too or married her and take the throne. Hak would be their bodygaurd and Soo-Won would be doing what he is doing right now.
If Soo-Won also killed Yona, damn, Hak would mess him up!!