Seo Kang-joon Returns to K-Drama with ‘Undercover High School’

Seo Kang-joon makes a long-awaited return to the K-drama scene with his next project, Undercover High School, an action-comedy drama.

Action-comedy K-dramas are cool! because their balanced storylines can be satisfying and memorable viewing experiences. A seamless interaction of their techniques achieves suspense, humor, and poignancy while adhering to a solid plot—looking forward to that in Undercover High School.

Written by Im Young-bin, the 12-episode series will be directed by Choi Jung-in. The plot hook follows a major incident arising in an operation that leads to the demotion of National Intelligence Service (NIS) star operative Jung Hae-sung (Seo Kang-joon). He is subsequently delegated to a secret mission at the elite Byeongmoon High School, where he goes undercover as a student and meets Oh Soo-ah (Jin Ki-joo), his homeroom teacher, shortly thereafter. 

Straightforward and attached to her students, Soo-ah starts noticing parallels between Hae-sung and her first love from childhood, who left her heartbroken and replete with unpleasant memories. Thus ensues a complex relationship between the two, perhaps a tense romance through dramatic suspense, where Hye-sung’s goal only serves to heighten the excitement.

Undercover High School seems even cooler, with an appealing woman getting involved with a tough man whose initially adversarial encounters ultimately mature into a growing attachment. The protagonists’ gradual journey of self-discovery, navigating misunderstandings and truth, is certain to reveal their strengths and weaknesses, leading to an awareness of their romantic feelings for each other. The marriage of animosity and fondness, ambiguity, and proximity in the story enables them to form a deep connection.

Hae-sung’s juxtaposition of emotional sensitivity and tough strength makes him such an intriguing, multifaceted character, one who, I feel, ably accommodates the intricacies of his own life while also engaging in intense action-packed episodes. Waiting for his (Seo Kang-joon’s) charisma to burst through on-screen.

Participating in Fantagio’s “Actor’s League,” Seo, now 30, became a member of the first-ever South Korean actor group, 5urprise. He later shot to fame for his portrayal in Cheese in the Trap (2016), and since then has performed in hit K-dramas, including Entourage (2016), Are You Human? (2018), The Third Charm (2018), Watcher (2019), When the Weather Is Fine (2020), and Grid (2022).

Before enlisting in the military, Grid was his last—a mystery sci-fi thriller series featuring General Affairs Bureau detectives—who, alongside Seo’s Kim Sae-ha, a bureau employee, are seen probing and pursuing an unnerving spirit who previously shielded humans amid an existential threat but resurfaced more than two decades later, letting a serial killer escape.

Following Grid, Seo Kang-joon resumes with MBC’s Undercover High School, slated for release in 2025, his first since he was discharged from military duty on May 22, 2023, after serving for 18 months as an active-duty soldier. For more information on him, read my Actor You Need to Know post.