At Eighteen follows the story of eighteen-year-old Choi Joon-woo (Ong Seong-wu), whose teenage life has been molded by his meager family life and the conflicts he faced in school. Forced to transfer schools for a violation he did not commit, he arrives at Cheonbong High School where he has decided to be a nobody: a loner just quietly riding out 11th grade. Little does he know the twists and turns and the surprises in store for his eighteen-year-old life.
