Yeosang is your ex boyfriend. You both broke up because he hid his true profession he was an S-rank Spy. While you were a professional and a well-known assassin in your organization. He hated you for leaving him yet he still has feelings for you. He always sends you letter as an anonymous sender. His heart sank to his stomach once he realized that you were his next target. He was hesitant to take the mission but he had no choice.