|“||I won't have any students slacking on my watch.||”|
Yungmuk is a senior student of the Hongmoon School who helps Master Hong Sokgyun train his juniors. He is a strict and by-the-book student who takes his training seriously as Master Hong's right-hand man. It took him eight years to become a formal disciple so he became envious of the new pupil when it only took him/her a few days.
Yungmuk was awake bright and early when he encountered Jinyung and the newest pupil nicknamed Cricket. He chastises Cricket for oversleeping and then sends the both of them to find Lusung. After the two leaves, he goes to meet up with Master Hong along with Gilhong and Hajoon.
Once Master Hong dismisses everyone to their training, Yungmuk goes with them to the school's Duel Hall to monitor their training. Cricket meets up with them later and tells Yungmuk that he/she has been officially accepted into the school. The Gon congratulates the new student along with everyone else and begins training Cricket in martial arts basics. Before Yungmuk could continue training Cricket, the pupil receives a letter telling him/her to train in the Proving Grounds. Yungmuk leads Cricket to the cave and says that he/she must enter alone.
Yungmuk waits for Cricket outside the cave until nightfall, when the school became under attack by Jinsoyun and her cohorts. Yungmuk runs off to help defend the school and ends up in a fight with Gubong. Despite his strength and skill level, Yungmuk was eventually killed by Gubong.