Undercover High School () is a 2025 South Korean action comedy spy television series written by , directed by Choi Jung-in, and starring Seo Kang-joon, Jin Ki-joo, and Kim Shin-rok. The series depicts a man who is an NIS agent goes undercover as a high school student. It aired on MBC TV from February 21, to March 29, 2025, every Friday and Saturday at 21:50 (KST). It is also available for streaming on TVING and Wavve in South Korea, and on Viu, Kocowa and Viki in selected regions.
Synopsis Jeong Hae-seong, a demoted NIS agent following a major incident that occurred during an operation, is tasked with a special mission of tracking down the whereabouts of Emperor Gojong's missing gold bars. Hae-seong hides his identity, goes undercover as a high school student at Byeongmun High School, and meets Oh Su-a, his homeroom teacher. Su-a, a devoted teacher to her students, begins to notice the similarities between Hae-seong and her childhood first love, who left her heartbroken and filled with painful memories.
Cast and characters Main Seo Kang-joon as Jeong Hae-seong / Jeong Si-hyun Yu Ji-wan as young Jeong Si-hyun An ace field agent of Domestic Team 4 of the NIS who is given a special mission to find Emperor Gojong's gold bars. Jin Ki-joo as Oh Su-a / Oh Bong-ja Park Seol-ha as young Oh Bong-ja Hae-seong's homeroom teacher who is a temporary Korean history teacher at Byeongmun High School. Kim Shin-rok as Seo Myeong-ju Chairwoman of the Byeongmun Foundation and Byeongmun High School who is Ye-na's mother.
Supporting NIS people Jeon Bae-soo as An Seok-ho Head of the Domestic Team 4 of the NIS and is like a second family and father to Hae-seong. Jo Bok-rae as Go Yeong-hun Hae-seong's junior agent at the NIS. as Park Mi-jeong Hae-seong's junior agent at the NIS. Lee Seo-hwan as Kim Hyung-bae Director of domestic division of the NIS. as Gong Jin-sang Seok-ho's classmate and the head of the NIS Domestic Team 1.
Student Council of Byeongmun High School Kim Min-ju as Lee Ye-na Student council president of Byeongmun High School who is Myeong-ju's only daughter. Park Se-hyun as An Yu-jeong Student council member of Byeongmun High School who is Seok-ho's daughter and Hae-seong's younger sister. Jang Seong-beom as Park Tae-soo A student council member of Byeongmun High School who is a son of a three-term National Assembly member from Yeouido. Lee Hyun-so as Han Seung-jae Student council member of Byeongmun High School who is a son of the CEO of Han Young Law Firm, one of the top law firms in South Korea. Yoon Chae-bin as Yoon Chae-rin A student council member of Byeongmun High School and an idol trainee. Kim Sun-min as Ji Hyun-joon Student council vice-president of Byeongmun High School.
Students of Byeongmun High School as Lee Dong-min A student of Byungmun High School who is bullied by Tae-soo's group. Jeong Soo-hyun as Im Yoon-cheol One of the class bullies that uses his mouth rather than fists. Kang Pil-jun as Son Beom-sik The class bully who has a keen eye for details. as Choi Su-jin A student who is faster and more sensitive to SNS and trends than anyone else. Kim Seung-beom as Kim Ho-jin A student of Byeongmun High School who is the source of information and is serious about internet broadcasting and content commercial production.
Teacher's office of Byeongmun High School as Park Jae-mun The principal of Byeongmun High School who is Myeong-ju's loyal henchman. as Baek Kwang-du, The vice-principal of Byeongmun High School. Lee Min-ji as Kim Ri-an Su-a's fellow teacher and soulmate who teaches physical education. Noh Jong-hyun as Lee Jun-ho Su-a's fellow teacher who has a crush on her and teaches mathematics.
Others as Im Cheong-ha Su-a's mother who runs Have a Drink With Su-a restaurant for over 10 years. Kim Soo-jin as Jang Man-ok Seok-hi's wife, Yoo-jung's mother, and a mother-like person to Hae-seong. Gu Min-hyuk as Kim Hyeon-ho Security guard at Byeongmun High School. Kim Eui-sung as Seo Byeong-mun A traitor to his nation who was never recorded in history and the keeper of Emperor Gojong's secret safe. Oh Eui-shik as Jeong Jae-Hyeon Hae-seong's father and a NIS agent who was missing for 22 years.
Production Development The series began its production and is planned by Namkoong Seong-woo, written by , directed by Choi Jung-in, and produced by Neo Entertainment and Slingshot Studios. In addition, it aimed to air in early 2025.
Casting In March 2024, Seo Kang-joon was reportedly in talks as the lead actor and his agency told the media that he was positively reviewing it. This was Seo's first work after completing his military service in May last year as well as comeback to the small screen after 2022 TV series Grid. In May 2024, Jin Ki-joo and Kim Min-ju were reportedly cast to work along Seo with the former as the female lead in the series. In June 2024, MBC confirmed that Seo and Jin would appear as the lead actors for the series. This was also Seo's first MBC drama comeback after appearing in Splendid Politics (2015). The same month, Kim Shin-rok was reportedly confirmed to cast July 2024.
Filming Principal photography began in the first half of 2024.
Original soundtrack Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Release MBC announced that Undercover High School would be broadcast in a Friday–Saturday timeslot in February 2025. The series was confirmed to premiere on MBC TV on February 21, at 21:50 (KST). It is also available for streaming on TVING and Wavve in South Korea, and on Viu, Kocowa and Viki in selected regions.
Viewership
+ Average TV viewership ratings Original broadcast date Average audience share(Nielsen Korea)Nielsen Korea ratings:
Nationwide Seoul 1 February 21, 2025 5.6% 5.8% 2 February 22, 2025 6.6% 6.5% 3 February 28, 2025 6.6% 6.7% 4 March 1, 2025 5 March 7, 2025 7.2% 7.0% 6 March 8, 2025 6.7% 7.1% 7 March 14, 2025 6.8% 6.3% 8 March 15, 2025 6.1% 6.1% 9 March 21, 2025 6.1% 5.8% 10 March 22, 2025 11 March 28, 2025 6.0% 6.3% 12 March 29, 2025 5.8% 5.8% Average In the table above, the represent the lowest ratings and the represent the highest ratings.
References
External links