The Dominator 3 - Junior Bullies.

Han-cheol, along with his gang, Geon-mo and Min-ho, tries to be the best in second grade. One by one, they beat out the talented second year students as if beating dojo masters. Han-cheol learns about a master, Jin-man, through a video. Without any idea what is going on, Min-su, wanting to practice finds a boxing ring where Jin-man also practices, and so begins to sleep with the two enemies. However, they need each other so they avoid their uncomfortable jealousies.