SPECIAL CLASSES OF MATH BETWEEN TWO OUTCASTS: A GENIUS MATHEMATICIAN WITH A HIDDEN PAST AND A NEEDY STUDENT GIVEN UP ON MATH Ji-woo (KIM Dong-hwi) an outcast in a prestigious private high school does not fit in due to different social backgrounds than his well-to-do classmates. One day he meets Hak-sung (CHOI Min-sik) the school's security guard who is actually a mathematical genius defected from North Korea now living with his past shut away. Ji-woo asks Hak-sung to teach him math and although reluctant at first Hak-sung eventually agrees to. Finding each other in their most difficult times Ji-woo and Hak-sung open up to one another during their special math lessons but their friendship is at risk when Ji-woo is framed for an incident in school and Hak-sung is faced with people prying on his past.