After completing his military service in 2023, Seo Kang-jun is back on the small screen with MBC’s new comedy-action drama “Undercover High School.”

The 31-year-old actor plays the role of Jung Hae-sung, who goes back and forth between being a National Intelligence Service (NIS) agent and a high school student in the Friday-Saturday drama, set to premiere tomorrow.

"I came back (to the entertainment scene) after over three years, and the world has changed so much, even down to the poses actors strike. But I'm confident I'll adapt quickly and deliver a great drama for the audiences," he said with a big laugh during a press conference at the broadcaster's headquarters in Seoul on Thursday.

The series centers on the ups and downs of an NIS agent who disguises himself as a high school student to track down the whereabouts of the missing gold bars of Emperor Gojong of the 1897-1910 Korean Empire. Seo is expected to show off his "all-around ace" persona with his outstanding judgment and excellent martial arts skills.

As for why he chose the project, he explained, "I've been drawn to this drama because it masterfully combines various genres like comedy, action, thriller and crime. While there are many easy-to-watch dramas, this one also has a deeper, thought-provoking layer."

He also shared the inner changes he experienced after his military service.

"The time in the military felt like an eternity ... I did a lot of thinking. I looked back on my past, thought about what kind of actor I am, why I want to act and what kind of actor I want to become," he said.

"Looking back, there's nothing I regret about the projects I've done or the path I've taken, even though everything might not have been perfect. I've always tried my best when making a choice. This time with 'Undercover High School,' I filmed it thinking, 'Let's do this without regrets. Whatever the outcome, whether the drama does well or not, I don't want to have any regrets."

The show is stirring interest with Seo's highly anticipated return to the small screen. While Director Choi Jung-in meticulously assembled the entire cast, her satisfaction with casting Seo has been particularly evident.

"For the 'handsome agent' setting, his looks were definitely a pass. But, while filming, I discovered even more charms. He's very honest, which suits his character well. I think (his personality) was reflected well in his acting," the director said. "I believe that acting details emerge from sincerity, and (watching his acting), I felt like he was truly living in that moment."

In the drama, Hae-sung, concealing his true identity, enrolls at Byeongmun High School and encounters his homeroom teacher, Oh Soo-ah (Jin Ki-joo). Soo-ah, dedicated to her students, finds herself drawn to Hae-sung, noticing striking resemblances to her first love, a painful memory from her past.

Jin takes the role of a temporary teacher with a heart full of love for her students as well as a burning passion to become a permanent teacher.

"Soo-ah is the character who is caught between her dedication to teaching and the realities that hinder her from fully realizing that dedication. I wanted to express more of the dilemmas of young adults in their early social life at that time, rather than Soo-ah being confined to the job of a teacher," she said. (Park Jin-hai/The Korea Times)