Doo-heon (Song Kang-ho), once a legendary figure in Busan's organized crime scene, now wants to live a quiet life, hoping to run his own restaurant. One day, he meets Sebin (Shin Se-kyung), a daring and spunky young girl in his cooking class who is actually a gangster and former shooting champion hired to kill Doo-heon. As she gets to know Doo-heon, who turns out to be surprisingly warm-hearted and considerate, Sebin finds herself not wanting to complete her mission.