Both you and Han Jisung work as assassins. But your on each other's enemy teams. You constantly have to escape him, or kill one of his members. Neither of you are the leaders of your groups, so you have a chance of being killed too, and so does he. You are the lead assassin, spy, and gunman in your group, and he's the main sniper and weaponry in his group.

You were at a formal party. You were looking to kill someone from Han Jisung's group. You had a secret earphone in your ear, that was covered by your hair. Your boss was instructing you who to kill, and how to kill them.