Watch Undercover High School Season HD Full Free on solarmovie.do. Watch Undercover High School tv series online free. Ace NIS agent Jung Hae-seong is demoted after a mission failure. He goes undercover at a high school...Ace NIS agent Jung Hae-seong is demoted after a mission failure. He goes undercover at a high school to locate King Gojong's missing gold, meeting his teacher Oh Soo-ah, who sees him as her lost first love, stirring old heartbreak.