Season 1

Ji Sung is a NIS agent working at Incheon Airport, and he is known for having sharp observation, judgment, and agility. Ji Sung falls in love with Myung Woo at a hospital he was admitted to for an injury he received during an operation, but they end up breaking up due to their career choices. After three years, he encounters Myung Woo again but becomes attracted to Do Kyung, after locking horns and resolving high-profile cases with her. Do Kyung is a confident businesswoman and the manager of the airport operation headquarters. Although Do Kyung didn't expect romance to bud from the get-go, at a certain point, she finds herself developing feelings for Ji Sung unexpectedly. However, subsequently finding out Myung Woo, who starts working as a doctor at the airport hospital, is Ji Sung's ex, she gets lost between love and friendship.