Undercover High School

Jeong Hae-seong, a demoted NIS agent following a major incident that occurred during an operation, is tasked with a special mission of tracking down the whereabouts of Emperor Gojong's missing gold bars. Hae-seong hides his identity, goes undercover as a high school student at Byeongmun High School, and meets Oh Su-a, his homeroom teacher. Su-a, a devoted teacher to her students, begins to notice the similarities between Hae-seong and her childhood first love, who left her heartbroken and filled with painful memories.