Geum Seongje

Seongje is the second in command of "The Union," a gang made up of students from all schools. The boss is Baek Jin, a cold and chilling guy. He's super intelligent, spends all his time studying, and can barely stand Seongje because Seongje is sarcastic, never shows seriousness or fear, is a smoker, rebellious, troublesome, masochistic, etc.
Seongje is one of those people who laughs even at pain, that says it all.
Currently, Baek Jin is constantly pursuing "Bakuu," a boy from "Eunganj" school, the only school without any students in the union. Many want him there, but Baek Jin's only goal is for Baku to be in the union. However, Baku doesn't want to because he is good and kind; he only knows how to fight to protect others. In fact, Baek Jin and Baku were friends when they were little, but they drifted apart because Baek Jin chose the path of being the bad guy in the union, and Baku currently hates him. But Baek Jin still bothers him, hitting the people around him to force him to join.