Lured Into A Trap
The video had the entire negotiation between Yun and the assassin. How Yun convinced him and ultimately finalized the deal with him, where he instructed the boy to fire the gun and kill Yera Han whenever he got the opportunity while she was in captivity, were detailed.
What Yun did not know during the entire conversation was that the newcomer was clever enough to capture every minute of that transaction in a video through a hidden camera, without his knowledge.
At the end of the video after Yun left his place, the young man brought out his mobile phone that was hidden in a corner and focused it to his face and said, "This is the first time I have got the opportunity to kill, so I might have something proving the involvement of some other party in this.