This Fresh K-Drama Hits 10% Peak Viewership, Tops Buzz Rankings for 2 Weeks

MBC’s Friday-Saturday drama 'Undercover High School' is drawing an explosive response from viewers.

In Episode 6, which aired on the 8th, the drama took a dramatic turn as Jung Hae-sung (Seo Kang-jun) and Oh Soo-ah (Jin Ki-joo) found themselves forced into an unexpected alliance after his identity was exposed. The episode recorded a 7.1% viewership rating in the Seoul metropolitan area and 6.7% nationwide, according to Nielsen Korea.

Notably, the heart-fluttering moment where Hae-sung and Soo-ah shared an umbrella in the rain saw ratings soar to 10%. The drama also dominated the 2049 viewership rating—the key demographic indicator for TV popularity—hitting 3.3%, making it the highest-rated program across all channels in its time slot and the most-watched show on Saturday.

'Undercover High School' was the only program across all channels to achieve a 3% rating in the 2049 demographic, a significant leap from its previous high of 2.8%. With its buzzworthy moments trending for two consecutive weeks, the show has firmly established itself as a favorite among younger viewers.

A Shocking Death and a Hidden Truth

The episode also delivered a major twist when security guard Mr. Kim (Koo Min-hyuk), who was supposed to meet Hae-sung, was found dead after falling from a rooftop following a struggle with an unidentified figure. Hae-sung arrived at the scene only to discover Kim’s lifeless body and, clutched in his hand, a notebook belonging to his missing father, Jung Jae-hyun (Oh Eui-sik).

As Hae-sung chased a suspicious man lurking nearby, he found himself in a rooftop brawl. Just as he was about to get the upper hand, a sudden noise from outside the door distracted him, allowing the assailant to escape. It was later revealed that the entire incident was orchestrated by Seo Myung-joo (Kim Shin-rok) and Park Jae-moon (Park Jin-woo), sending shockwaves through the audience.

Later, Hae-sung confronted Director Kim (Lee Seo-hwan), gripping him by the collar while demanding to know why the security guard had possession of his father’s notebook. As the pieces fell into place, Hae-sung realized that his father’s final mission was the same as his own—and that the truth about his disappearance had been deliberately concealed.

A Mysterious Clock and a Tense Confrontation

Determined to uncover more secrets, Hae-sung turned his attention to an old grandfather clock in the student council room. Using keywords from his father’s notebook, he unlocked a hidden mechanism inside the clock, which triggered a haunting playback of Byungmoon High School’s anthem. Just as he recorded the sound and prepared to leave, Soo-ah appeared, intensifying the suspense.

Soo-ah, having witnessed Hae-sung on the rooftop the night of Kim’s death, voiced her suspicions, raising the stakes. In a bold move, Hae-sung finally came clean, revealing that he was a National Intelligence Service (NIS) agent on an undercover mission. With this revelation, viewers were left wondering how their relationship—and the mission—would evolve.

The Mystery of the Grand Piano

Hae-sung also dug deeper into the school’s third urban legend, which revolved around a grand piano. Thanks to Soo-ah, he learned that a 1950s grand piano was stored in the chairman’s office. The duo devised a plan to infiltrate the office during the school event, “Byungmoon Night.” However, Hae-sung was barred from participating due to accumulated demerits. To overturn this, Soo-ah humorously entered him in the school’s promotional model contest, a moment that had viewers laughing out loud.

A Romantic Twist in the Rain

The episode’s final scene left fans swooning as Hae-sung and Soo-ah shared an intimate moment in the rain. After drinking at Soo-ah’s mother’s restaurant, they stepped outside only to be caught in a sudden downpour. Soo-ah’s mother handed them an umbrella, casually calling out, “Oh Bong-ja! Umbrella!”—a name that triggered a childhood memory for Hae-sung. As they huddled under the umbrella, a passing motorcycle splashed water toward them, prompting Hae-sung to instinctively pull Soo-ah into his arms, sending viewers’ hearts racing.

With Hae-sung’s secret now exposed and an alliance forming between him and Soo-ah to unravel the school’s mysteries, Undercover High School continues to deliver an exhilarating mix of action, suspense, and romance.

The drama airs every Wednesday and Thursday at 9:50 PM KST. As an original series with no pre-existing source material, viewers can find detailed character relationships and plot summaries on its official website.