Kye Doo-sik (Jung Joon-ho, who is usually associated with more serious action fare, such as "The Siren" and "Last Witness") is the second-in-command of a mob gang. Though he has successfully expanded his boss' territory by defeating a rival gang, he is prevented from moving up in the criminal organization due to his lack of a high school diploma. It seems that all his contemporaries have at least a high school education, with some having even attended college, and Doo-sik's lack of formal education is downright embarrassing-- he is even oblivious to the existence of the Internet and has yet to discover what an e-mail address is. Thus, Doo-sik is given an ultimatum by his boss (Kim Sang-joong)-- he must go back to school and graduate if he wants to continue as a gangster.

The first half of "My Boss, My Hero" is clearly a 'fish out of water' comedy, as Doo-sik is knocked to the bottom of the food chain at his new school. Coupled with the ineptness of Ka-ri, who consistently gives Doo-sik bad advice about how to fit into his new environment, there are more than a few well-earned chuckles to be had. In addition, the film makes some pointed comments about the brutality of the Korean education system, a sometimes-dangerous place where corporal punishment still exists and the pressure to perform leads to all sorts of abuses and criminal behavior (apparently, the story is loosely based on an actual incident at a Seoul high school). Unfortunately, there are a number of instances where the script strains credibility, such as Doo-sik being bullied by the local toughs, particularly since he easily stands a head taller than them and is almost a decade their senior. In addition, this first half also suffers from some choppy editing, which makes a number of the scene transitions particularly jarring.

However, the film really takes off in the second half, where the story sheds the laughs and presents Doo-sik's heart-wrenching struggle to help the teachers and students overthrow the school's corrupt administration. As the principal's underworld connections arrive to break up a peaceful protest, director Yun Je-gyun pulls no punches in showing the brutality that ensues. In addition, the film's second half also features a beautifully rendered fight sequence that takes place in a torrential downpour, reminiscent of the opening action sequence in "My Wife is a Gangster".