Choi Jihoon is assigned to Daehun High School, the worst high school in Korea. He pledges to be the ‘Jjang (Top gangster)’ here, but the reality is quite tough.

Na Dae Gi was the leader of a student gang and had power over all high schools in his area. He declares the gang's disbandment, goes into a third-degree College of Education to become a teacher, and finds a job in Kangho High, which has a reputation for being highly populated with troublemakers. The student gangs at Kangho High, who all the other teachers have given up on, start a fight with Dae Gi, who prepares a lesson of his own, and so begins the war between the gangster teacher and the student gang at Kangho High.

There is an unprecedented “Special Squad”, commissioned to solve the unsolved incidents that even the police can’t handle. Those who have raided the underage prostitution case will be commissioned to investigate the ‘Algo Mall’ mission. What they’ve thought to be just one of the usual cases of underaged labor, there seem to be a huge background at the end of the dark underworld… Here comes the crazy ones who beat the bad guys!