Synopsis: In "Undercover High School" Season 1, Episode 6, airing March 8, 2025, Jung Hae-seong (Seo Kang-joon) reels from the security guard’s death, clutching a notebook left by his missing father. Confronting his NIS chief, he learns his father hunted the same gold decades ago. Oh Soo-ah (Jin Ki-joo) catches Hae-seong fighting on the rooftop, demanding answers about his identity and the guard’s “suicide.” Hae-seong deflects but later apologizes at her mom’s restaurant, securing her reluctant help. A tender moment hints at trust, but the mission darkens as betrayal looms.

Review: Episode 6 deepens the mystery with Hae-seong’s family ties. Soo-ah’s suspicion spices the drama, though her quick alliance feels convenient. A gripping 8.5/10.