In 1983, the South Korean president and his delegates are visiting Burma when a bomb planted by North Korean agents explodes, killing some high-ranking officials. This historical event is called the Rangoon bombing (also known as the Rangoon incident). To strike back, five South Korean officials plan a covert operation, codenamed "Operation Cleansweep," to enter North Korea and kill several top members of the North's high command. Lee Jin-pyo and Park Moo-yul, two Presidential Security Service bodyguards and best friends who were present at the bombing, organize a 21-man team for the mission. However, as the team wreaks havoc in Pyongyang, the five officials abort the plan to avoid an international crisis if the mission is discovered. Their major concern is that the United States will withdraw its nuclear protection if the mission is made public, in light of Seoul's official declaration that it will not retaliate.
The operation is successful, but as the troops swim out from Nampo to an ROK Navy submarine assigned for their extraction, snipers aboard the submarine open fire on them. An already injured Park sacrifices his life to save Lee. Lee swims back to shore and returns to South Korea, where he finds out that the assault team's service and personal records have been erased.
Promising to avenge his fallen comrades, Jin-pyo kidnaps Moo-yul's infant son, and names him Lee Yoon-sung. He flees to the Golden Triangle to raise the child as his own and trains the boy intensively in combat. Following an attack on a village they are living in, Jin-pyo confesses his long-term plan for revenge to a teenaged Yoon-sung.
Seven years later, after successfully finishing his education and attaining a doctorate in the United States at the Massachusetts Institute of Technology, Yoon-sung returns to South Korea to fulfill his adoptive father's plan for revenge. He enters the Blue House as an IT expert under the National Communication Network Team. He is warned by Jin-pyo not to trust anyone and never fall in love, as doing so will put the people around him in danger.
While working at the Blue House, Lee meets bodyguard Kim Na-na. Eventually Na-na participates in his revenge plan, as they discover that they have the same goal in mind. Problems occur as Jin-pyo's revenge plot unfolds, especially when Lee defies his surrogate father at several occasions as they try to identify and kill the officials, known as the "Council of Five."
Each member of the Council have achieved significant wealth and political influence since 1983, and are engaged in various levels of corruption. Jin-pyo and Yoon-sung's conflict stems primarily from Jin-pyo's wish to murder each official, and Yoon-sung's wish to teach them a lesson and expose their corruption without killing them. As Yoon-sung exposes the officials' corruption, the citizens of Korea sense an unseen force of justice that they dub "City Hunter."
Lee Min-ho as Lee Yoon-sung/Poochai
Codenamed "City Hunter", Yoon-sung's ultimate goal is to avenge his father's killers. Using the identity of a Korean-American teenager, who is later revealed to have died several years before, he assumes a double life by graduating from MIT with a doctorate degree and lands a job at South Korea's presidential palace. It led him to cross paths with presidential bodyguard Kim Na-na, with whom he falls in love.
Forced to take care of herself at an early age after her mother was killed in a drunk driving accident and her father became comatos, she is independent and strong-willed. Her exceptional skills in martial arts eventually earns her an assignment with the Presidential Security Service. During her time as a bodyguard, she falls in love with Lee Yoon-sung and eventually discovers his real identity.
Lee Joon-hyuk as Kim Young-joo
An intelligent prosecutor, Kim Young-joo possesses a strong sense of justice, even against the corrupt politicians of South Korea. He is the son of one of the members of the "Council of Five." He is a constant rival of City Hunter, working towards the same goals under legal cover, while trying to figure out his identity at the same time. Young-joo dies trying to arrest Chun Jae-man in the penultimate episode.
Operation Clean Sweep's sole survivor, Lee spends the mediate years in the Golden Triangle as a drug lord. Full of anger, he wants to kill all of the people who ordered his team dead. He pretends to be a Korean-American investor and uses Lee Yoon-sung as his agent of vengeance. He is killed by the Presidential Security Service in the final episode after failing to kill President Choi. Lee and the rest of the Clean Sweep strike team are eventually honored in Seoul National Cemetery.
A problem gambler but a very good cook whom Lee Yoon-sung saves from thugs in Thailand and later becomes his close friend. Over the course of the series, Bae and Lee become partners under Lee Jin-pyo's scheme – and also racks up huge debts buying stuff from the home-shopping network. However, it is revealed that Bae witnessed the accident that resulted in Kim Na-na's woes and was hiding in Thailand by the start of the series after being paid off by the culprit – Kim Jong-shik, a member of the Council of Five – to change his story. Bae decides to start a new life in the United States with Kyung-hee by the end of the series.
One of President Choi's two children, Da-hye is smitten with Lee Yoon-sung early in the series and requests him to be her tutor. Her status of being the president's daughter does not win her any friends at school and even creates a public scandal when she attacks a group of girls who criticizes her father's governance within earshot. She decides not to go to college (because of her poor grades) and is forced to find a job, and later falls in love with Kim Young-joo.
The incumbent president of South Korea, Choi was one of the five men involved in planning the 1983 operation and promised the unit he will help get them home. He was later out-voted in the decision to abort the operation and forced to live with the guilt for 28 years. He is the only member of the group who knows that Lee Jin-pyo survived the debacle, yet does nothing to stop him despite knowing that the former bodyguard's ultimate goal is to kill him and the other officials. It is later revealed that the president is Lee Yoon-sung's real father, who sired him with Lee Kyung-hee. He is depicted in the series as an idealist who believes the end is worth the means, which results in his impeachment by the National Assembly after he bribed a number of deputies to help pass an important education reform bill.
Lee Yoon-sung's father, who dies protecting Jin-pyo in the first episode. It is revealed that he is not Yoon-sung's real father, and was merely protecting Lee Kyung-hee after her affair with Choi Eung-chan ended. Park and Lee Jin-pyo's names are at the top of a memorial slab honoring the Clean Sweep team.
Lee Yoon-sung's mother, who went on to lead a solitary life running a small eatery after Yoon-sung was kidnapped as an infant. She had become pregnant with Choi Eung-chan's child, but when she decided to keep the baby, her life and the baby's was threatened by Chun Jae-man. She contracts leukemia later in the series, but starts to recover after Yoon-sung donates bone marrow to her. Kyung-hee travels to the United States with Shik-joong to start a new life in the final episode.
A former police officer, Kim is tapped by Jin-pyo for the revenge project upon learning that his own brother was part of the 1983 operation. He was sacked from the force for breaking into the National Intelligence Service's files while trying to find out what happened to his brother.
A senator, Kyung-wan is the City Hunter's first target among the Council of Five, who also pocketed certain children's welfare funds. He is imprisoned for the crime, but is implied to have died at Jin-pyo's hands in Episode 9.
A businessman running a chaebol (a chemical company and hospital is seen in the series as part of it), Jae-man participated in planning the North Korea mission. He is the most corrupt and ruthless member of the Council of Five. He later burns a book containing all covert operations in 1983 that were supposed to be declassified in 2030. It is revealed that the book he burned was just a copy and Jin-pyo acquired the original document, but not before Jae-man does a little historical revisionism by saying that the operation took place because the team tried to defect to the North with some state secrets. His corruption case is also depicted as one that no government prosecutor wants to handle, as those who do take it on are often harassed into quitting. Chun dies at Jin-pyo's hands in the final episode.
Kim Young-joo's father and a former education minister, Jong-shik was one of the officials who plotted the North Korea mission and agreed to the subsequent cover-up. He also killed Kim Na-na's mother and gravely injured her father while drunk-driving, and pays off a witness (Bae Sik-joong) to say that Na-na's parents were at fault for the accident. He would become comatose later in the series as the City Hunter tries to take him down in light of an investigation over hiding around two billion won in college subsidies. He regains consciousness in the final episode to learn of his son's death.
Choi Sang-hoon as Seo Yong-hak
A former defense minister and a prospective presidential contender, Yong-hak was an army general at the time of the 1983 operation and has often used his influence to have his three sons avoid the military's required three-year conscription. The City Hunter unmasks him for entering into deals to provide substandard combat boots and acquire defective fighters for the Air Force. As the truth behind Clean Sweep unravels, Yong-hak comes forward with what he knows and pins the president as the mastermind.
The series has received positive reviews and was also a commercial success selling out advertisement space at a high price of $420,000 per episode.
Lee Min-ho's role netted him Best Actor at the 4thKorea Drama Awards, as well as an endorser for the Hyundai Veloster in China. He would later be recognized by the Seoul Prosecutor's Office as an "Honorable Prosecutor" in a ceremony on January 4, 2012.
In between December 2011 and January 2012, the Asian-American Donor Program partnered with the Transplant Informers blog to run a special raffle for a full DVD boxed set of the series, as part of an awareness campaign for bone-marrow transplants. The promotion was held to recognize the show's authentic depiction of a bone-marrow transplant (when Yoon-sung had to donate some for his mother).
Before the series aired the broadcast rights were exported to several countries such as the U.S., Hong Kong, Thailand, Romania and Vietnam. At the time other countries such as Japan, Taiwan, Bulgaria, the Philippines, and Kazakhstan were also actively seeking to acquire the dramas broadcast rights. In the United States the drama was made available for streaming with English subtitles on Hulu.
Philippines – The ABS-CBN network aired the show dubbed in Filipino during primetime from January 23, 2012 to April 13, 2012 replacing My Binondo Girl. A rerun called "City Hunter Returns," aired in the network's "Kapamilya Gold" afternoon program lineup from July 9, 2012 to September 7, 2012.
Japan: Fuji TV from February 6 to 29, 2012 five episodes a week for an hour at 2pm. The series aired in Japan in the same time-slot as Lee Min-Ho's previous drama Personal Taste which was airing on TBS. The series was then rerun again starting March 29, 2012 on cable channel BS Fuji on Tuesdays at 7pm. The series also re-aired on cable channel KNTV from November 6, 2012 to January 8, 2013 in Korean with Japanese subtitles.
Malaysia: 8TV January 10, 2013 on Mondays through Friday's at 8:30pm.
Singapore: MediaCorp Channel U from December 30, 2012 to May 26, 2013.
Hong Kong: TVB from July 2, 2012 to August 7, 2012.
Indonesia: Indosiar February 14, 2012 on Tuesdays at 4:30 pm,RTV April 27, 2015 on Monday to Friday at 2:00 pm
Algeria: City Hunter aired on DTV starting 2015, dubbed into Arabic as قناص المدينة (Qannāṣ al-Madīnah).
France: GONG February 5, 2012 on Sundays at 9:40PM