Abandoned by his mother shortly after immigrating to America, Gon is raised by the mafia and grows up to become a cold-blooded hitman. Though usually flawless in taking out his targets, Gon makes a terrible mistake of killing an innocent young girl. Swamped by feelings of regret, guilt and shame, Gon no longer wants to be a hitman, but his boss gives him one last mission. So Gon finds himself in Korea, the land of the mother that abandoned him, on the trail of his last target. But in bitter irony, that target is Mo-gyeong, the mother of the dead child.

Assistant TV commercial director Choi Bo-Na is tasked with doing anything and everything at work. Due to overwork her appearance is always a complete mess, she also hasn’t dated in many years.