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".
Ji-hwan and Dal-rae are age-old friends who have grown up in the same neighborhood. They share almost 13 years of childhood and adolescence, but they do not think of each other as a romantic partner because they know each other too well.
As they struggle to realise their dreams - one desires to be an actress but she has to overcome her timidness; and the other wants to be a stuntman like his idol Jackie Chan - they notice their friendship isn't as it used to be when Dal-rae gets a boyfriend ...
Ju Young-ju, an beautiful ex-con artist who has been recently released on parole, is planning to attend her sister’s weeding. On her way she crosses path with Choi Hee-chul, a shy and unsure young man who is on his way to see his girl friend in Seoul. By a small series of unexpected events, the precious ring that Hee-chul planned to give to his girl friend end up in Young-ju possession, which at the same time, loose her bag. With only information she had chance to gather on Choi Hee-chul, she decides to find him, give him back the ring and take back her bag. However, at the moment of giving back the ring, her old lying habit kick back and obviously, hilarity and adventure ensues.
Ji-won (Kim Ha-neul) is a college student stricken by selective amnesia due to a near-drowning experience. The missing memory seems to suggest that she was a close friend with another girl (Nam Sang-mi), but the details remain fuzzy. Meanwhile, her friends, members of a high school clique, are beginning to turn up as dead bodies.
Please note that this movie is rated R and may contain material not appropriate for all ages.