MBC’s Friday-Saturday drama Undercover High School delivered a game-changing sixth episode as Jung Hae Sung (Seo Kang Joon) began an unexpected alliance with Oh Su A (Jin Ki Joo) after she discovered his true identity.
The episode recorded 6.7% viewership nationwide according to Nielsen Korea, with ratings peaking at an impressive 10% during the romantic finale scene.
Episode 6 featured a shocking development when security guard Mr. Kim (Goo Min Hyeok), who had planned to meet Hae Sung, died after falling from a rooftop following a mysterious fight. Soon after, Hae Sung discovered his father’s notebook and pursued the mysterious assailant but ultimately lost him. The plot revealed this incident was orchestrated by Seo Myung Joo (Kim Shin Rock) and Park Jae Moon (Park Jin Woo).
Seeking answers, Hae Sung confronted Director Kim (Lee Seo Hwan) about the notebook’s significance, realizing his missing father’s final mission mirrored his own. Later, he decoded clues hidden in a grandfather clock and attempted to uncover Byeongmun High School’s secrets, only to encounter Su A in the student council room, creating palpable tension.
Su A, suspicious about Hae Sung’s presence on the rooftop during Mr. Kim’s death, confronted him about his identity. In response, Hae Sung revealed himself as a National Intelligence Service agent and confessed everything.
He finally revealed his true identity! #UndercoverHighSchoolEp6 #UndercoverHighSchool pic.twitter.com/QRCVYgRgc2
— ChingusOfKDrama (@ChingusOfKDrama) March 9, 2025
The pair, while investigating rumors related to a grand piano, devised a plan to infiltrate the chairman’s office during the upcoming “Night of Byeongmun” event.
Seo Kang Joon really did peak in comedy-ing for his role as an undercover highschool student. #UndercoverHighSchool #UndercoverHighSchoolEp6 pic.twitter.com/7pES0jRyvx
— Trish 🌸 (@tamtamtami16) March 8, 2025
The episode concluded with a swoon-worthy scene as Hae Sung and Su A shared an umbrella in the rain, growing closer. Hae Sung was startled when he heard Su A’s mother calling out “Oh Bong Ja! Umbrella!”—reminding him of a childhood friend.
HIS EXPRESSION WHEN HE REALIZED THAT SUA IS INDEED HIS FIRST LOVE?!?!?!!! OH I AM DEFINITELY GOING INSANE WAITING FOR THEIR DATING ERA 😭😭😭🫵🏻#UndercoverHighSchool #UndercoverHighSchoolEp6 pic.twitter.com/kznvU1QFCK
— liy (@chaedaely) March 8, 2025
Omg, I just realized that Haeseong was in love with Oh Sua when they were kids, but Oh Sua fell in love with Haeseong as an adult 😭 It’s so CUTEEE#UndercoverHighSchool #UndercoverHighSchoolEp6
— Ze (@enjoydiamant) March 9, 2025
When a passing motorcycle threatened to splash them, Hae Sung pulled Su A into his arms to protect her from the water.
Undercover High School airs every Wednesday and Thursday at 9:50 PM KST.
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