# Undercover High School

Undercover High School (Korean: 언더커버 하이스쿨) is an ongoing South Korean action comedy spy television series written by Im Young-bin [ko], 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 premiered on MBC TV on February 21, 2025, and airs every Friday and Saturday at 21:50 (KST). It is also available for streaming on TVING and Wavve in South Korea, and on Viu and Kocowa in selected regions.

## Synopsis

Jeong Hae-seong, an NIS agent who was demoted after a major incident that occurred during an operation, and later he 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
    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
    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
    The head of the Domestic Team 4 of the NIS and is like a second family and father to Hae-seong.
* Jo Bok-rae [ko] as Go Yeoung-hun
    Hae-seong's junior agent at the NIS.
* Yoon Ga-i [ko] as Park Mi-jeong
    Hae-seong's junior agent at the NIS.
* Lee Seo-hwan [ko] as Kim Hyung-bae
    Director of domestic division of the NIS.
* Im Cheol-hyeong [ko] 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
    The student council president of Byeongmun High School who is Myeong-ju's only daughter.
* Park Se-hyun [ko] as An Yu-jeong
    A student council member of Byeongmun High School who is Seok-ho's daughter and Hae-sung's younger sister.
* Jang Seong-beom [ko] 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
    A 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
    The student council vice president of Byeongmun High School.

#### Students of Byeongmun High School

* Shin Jun-hang [ko] 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
    A student of Byeongmun High School who is a bully that uses his mouth rather than his fists.
* Kang Pil-jun as Son Beom-sik
    A student of Byeongmun High School who is a bully that has a keen eye for detail.
* Shin Ga-eun [ko] 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

* Park Jin-woo [ko] as Park Jae-mun
    The principal of Byeongmun High School who is Myeong-ju's loyal henchman.
* Oh Yong [ko] 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

* Kim Young-ah [ko] 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 who got missing when Hae-seung was 9

## Production
### Development

The series began its production and is planned by Namkoong Seong-woo, written by Im Young-bin [ko], 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 would be Seo's first work after completing his military service in May last year and also his comeback to the small screen after Grid (2022). 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). On the same month, Kim Shin-rok was reportedly cast and was confirmed to appear in July 2024.

### Filming

Principal photography began in the first half of 2024.

## 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 and Kocowa in selected regions.

## Viewership

| Season | Season | Episode number | Episode number | Episode number | Episode number | Episode number | Episode number | Episode number | Episode number | Episode number | Episode number | Episode number | Episode number | Average |
| Season | Season | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | Average |
| | 1 | 1.099 | 1.311 | 1.199 | 1.537 | 1.387 | 1.386 | 1.312 | 1.239 | TBD | TBD | TBD | TBD | TBD |
Average TV viewership ratings :
| Ep. | Original broadcast date | Average audience share (Nielsen Korea) | Average audience share (Nielsen Korea) |
| Ep. | Original broadcast date | Nationwide | Seoul |
| 1 | February 21, 2025 | 5.6% (12th) | 5.8% (9th) |
| 2 | February 22, 2025 | 6.6% (5th) | 6.5% (4th) |
| 3 | February 28, 2025 | 6.6% (9th) | 6.7% (6th) |
| 4 | March 1, 2025 | 8.3% (3rd) | 8.3% (3rd) |
| 5 | March 7, 2025 | 7.2% (6th) | 7.0% (6th) |
| 6 | March 8, 2025 | 6.7% (3rd) | 7.1% (3rd) |
| 7 | March 14, 2025 | 6.8% (6th) | 6.3% (8th) |
| 8 | March 15, 2025 | 6.1% (4th) | 6.1% (3rd) |
| 9 | March 21, 2025 | | |
| 10 | March 22, 2025 | | |
| 11 | March 28, 2025 | | |
| 12 | March 29, 2025 | | |
| Average | Average | — | — |
| In the table above, the blue numbers represent the lowest ratings and the red numbers represent the highest ratings. ||||