Kil-Sung is a young man with an eye patch covering his right eye. He has a shoulder-length hair that he ties on half ponytail and bangs mostly collecting to the right side of his face that further covers his already hidden eye.
Similar to his fellow soldiers, he wears a cape with shoulder pads over an armor held by a belt. He also dons a trouser and a pair of boots on the bottom. He hangs his sword on the right side of his belt.
He is a loyal and supportive soldier who follows Tae-Jun’s orders without hesitation. However, he deems himself as inferior due to being a servant, and doesn’t like to put his master in trouble by his fault.
Kil-Sung, together with the other officers stationed at the southern government office, welcomes Kan Tae-Jun and his aide, Heuk-Chi to their headquarters who were ordered to capture the bandit group interfering with their tax collection. They thought that since Tae-Jun arrived, they will be able to resolve the problem, but they find him useless as he is suffering from lethargy. They receive a report that the bandits are on the move again, and they all go to Katan. They search the village for the tax that was stolen while looking for the thieves. After a while, he finds the tax hidden and tells it to everyone.However, a man soars towards them and attacks them from above. Following this, a man with a huge hand appears before them and attacks them as well, rendering them all knocked to the ground. Tae-Jun is pinned down by the soaring man, but by some miracle, he becomes motivated to move and overpowers the enemy. Kil-Sung is surprised and inspired from this event. Despite this moment however, they are all soon thrown out by the man with huge hands.
They return several times to the village, but they are always thrown out by the bandits. Because of this, Tae-Jun decides that he will work undercover as a normal citizen so that he can enter the village. Kil-Sung quickly tells him that they will do it for him, but instead Tae-Jun insists to do his plan by himself. Inspired once more, they support their master and give him a firework so he can signal them about the bandits. While they wait for Tae-Jun’s signal, they station themselves near Katan. As night falls, the firework has been launched and Kil-Sung immediately orders to fire the front of the village. In the midst of the attack, he sees someone running and finds out that Tae-Jun is crawling back to them. They stop their attack after learning that their master drops the firework by accident and the bandits are no longer there.
Tae-Jun continues conducting his investigation, and in the meantime, they check Katan once more. Kil-Sung sees Heuk-Chi check a house, whose owner quickly shut the door at him. He accompanies him inside the house and they find an old lady who condemns their entering without permission. He ignores her and instead looks at a suspicious bulging bed. He believes that the old lady must have been harboring bandits there and approaches the said object. However, the old lady stops him as she tells him that her husband, who has an infectious disease, is sleeping there. Scared of getting ill, he suggests to Heuk-Chi for them to get out already.
That night, Kil-Sung gets a massage from Tae-Jun, but to his surprise, the massage is rather stiff and uncomfortable. He asks him if he is massaging him for gratitude for their hard work, but thinks otherwise as he knows that his master won’t do such a thing. Tae-Jun squeezes his shoulder hard again, and he suffers from pain. Another officer tells Tae-Jun how to massage properly, and demonstrates it to him. However, as Tae-Jun tries it again, he isn’t able to do it properly. Out of a sudden, Tae-Jun asks where he lives and if ever he wants to go back there. Kil-Sung replies that he is from the east and he doesn’t want to go home anymore as he thinks that his parents are probably dead. Tae-Jun then questions his status and its unfairness, but Kil-Sung affirms him that he is born for the sake of the growth of the Fire Tribe.
Several days later, he and everyone receive orders from Tae-Jun to set up a clinic to a village where he found the bandits. While doing their job, Kil-Sung falls ill and is taken care of by his master on his room. Feeling ashamed of his state, he apologizes to Tae-Jun as he brings an illness to his room and promises that he will kill himself if ever he will get infected.However, Tae-Jun asks him not to worry and even remembers his name. After his recuperation, Kil-Sung returns to duty once more and they are ordered to set up another clinic at Enri Village. Everyone becomes doubtful about the order, but Kil-Sung tells them that he will follow the order as he doesn’t think of Tae-Jun’s goal to be a waste of effort. Since then, all of them work together to achieve what their master wants.
Soon before the war between Sen and Kouka starts, he follows Heuk-Chi together with his comrades and protects Tae-Jun from the Sen's army who are passing to the village they are currently staying at.
Due to the kindness of Tae-Jun, Kil-Sung manages to overcome his disease and therefore, he is grateful to him for the care and attention he received from him even if he is just a mere servant. From then on, he follows Tae-Jun’s order without hesitation.
- Akatsuki no Yona Chapter 58, Page 16
- Akatsuki no Yona Chapter 53, Page 16
- Akatsuki no Yona Chapter 56, Page 4
- Akatsuki no Yona Chapter 57, Page 20
- Akatsuki no Yona Chapter 57, Page 25
- Akatsuki no Yona Chapter 57, Pages 26-27
- Akatsuki no Yona Chapter 58, Pages 16-17
- Akatsuki no Yona Chapter 59, Pages 5-6