This drama is about two daughters who get ownership of their father's restaurant, and someone who sets about looking for a piece of his past, working together.
Three months before the presidential nominating convention, Jang Il Joon, from the New Wave Party, declared his candidacy. On that same day, a woman died in a gas explosion in Sam Chuk. Yoo Min Ki, a documentary producer, heard of his mother's sudden death and headed back home. As he cast his mother's ashes in the sea, he thought of his childhood: his father always blurted out that Min Ki was not his son whenever he was drunk. After the funeral, Min Ki returned to Seoul and Jang Il Joon asked Min Ki to work as a PR agent to record the election campaign process. When Min Ki asked Il Joon why he was chosen, Il Joon confessed that Min Ki was his son. Min Ki soon begins to suspect that his mother's death was not an accident and that Il Joon had actually killed her.
Ryu Hae-Kuk (Park Hae-Il) enters a reclusive country village to attend his father's funeral. During his stay he investigates the death of his father and uncovers what appears to be a conspiracy. Why do the villagers act so strange? Why do they keep asking him when he will return to Seoul? The man then confronts the village leader Cheon Yong-Deok (Jeong Jae-Yeong). The secrets of the village then start to unravel ...
Disguised as a travel agent, “Su-ji” is a government spy with six years’ experience who can’t reveal her career to her boyfriend “Jae-joon.” After she lies again, her boyfriend breaks up with her and leaves without notice, leaving her struggling alone with her sadness. Three years later, while chasing an industrial spy in disguise as a cleaning lady, she happens to run into Jae-joon. He’s become an international certified accountant, and seeing him throws her feelings into doubt. Jae-joon has become tired of his girlfriend’s constant and suspicious lies. In one phone call, he tells her he’s leaving Korea to study in Russia. Three years later, disguised as a distinguished international accountant, he enters the NIS (National Intelligence Service) as an agent in its overseas branch. He’s a newbie who got a late start, but he’s highly motivated and takes off on his first field mission, chasing a Russian crime organization, when he runs into Su-ji. It’s shocking to see her now as a hotel cleaning lady, but his affections for her are as strong as ever… Lying is part of the job, secrecy is the name of the game in "My Girlfriend is an Agent".
Jun-oh, formerly a bank employee, gets a call on his first day at work from a woman seeking advice. She asks if insurance is paid out on suicides, and only after hanging up does he see the warning on the insurance agreement. A few days Jun-oh receives a request for a meeting with an unknown policy holder. From the living room of a decrepit house Jun-oh opens the door to the bedroom to see a seven-year-old hanging from the ceiling. Police start an investigation, but the autopsy and all the evidence points to suicide. But Jun-oh can’t shake his suspicions that the incident was actually a murder. Believing that insurance, which should protect lives, cannot be seen to promote murder, he withholds payment. There is evidence of other serial murders, and a secret lying inside company records in storage. Where is the truth? And what is the true nature of the Black House?