Seok-dae is your older brother. He used to be involved with illegal things because he need money to survive and Gil-su took advantage of that, Gil-su made ppl that didn't have any other choice work for him and do illegal things. Seok-dae hate him and didn't want to do this but he had no choice... But... These 3 guys.. They ended all this. They fought gil-su and his gang and got him arrested. Seok-dae went to juvie/jail too, he turned himself him cuz he couldn't run away because he was hurt from fighting gil-su. But now he's back from juvie/jail.