Judge O is a bit shorter than the rest of the Judges, and has a wiry frame and is mainly seen wearing the Judge's uniform. He has white, shoulder-length hair and dark-colored skin. O states that his skin color is the result of being burnt and his hair color being bleached by Chang-Sik's flames. He orignially had pale skin and brown hair in his youth.
Seventeen years after the events of RagnarÖk, O has cut his fringe diagonally. Other than this, he retains his original appearance.
Judge O has a very calm and composed personality and can be happily perky, as opposed to Judge Q's rash behavior or Judge R's irritability. He is often the one who mediates between them (Judge Q and Judge R) and keeps them from fighting at the wrong time. He seems to be prideful of being a Judge and was very angry about hearing Announcer Shim's death by Drake McDonald, going as fas ar to swear revenge. He is also somewhat afraid of/ traumatized by Yu Mi-Ra after seeing her mercilessly dislocate the necks of all the thugs attacking her.
He cares for his dragons, rescuing Chang Sik (in humanoid form) from Xiao Chen and is concerned when the dragons under his command fight a lot. Because of Xiao Chen's history of butchering dragons O bears a grudge against her, as his dream is to create a world were humans and dragons can live together in harmony.
As a child O had difficulty establishing emotional connections with other people, but related to animals easily. This trait of his allowed him to sense Changsik's existence long before they had ever met, and what let him seek her out to make her his friend/power.
Judge O visited Yu Mi-Ra's school only to find her beating up thugs ruthlessly. O then invited Mi-Ra to the God Of High School Tournament but refused to make eye contact due to his fear of her. When all the Judges were at the tournament to oversee the fight, Judge Q and Judge R end up almost having a fight, but O got between them and told them if they don't act nice, he will not be quite which got both Judge to stay cool while O mentions that Mi-Ra is the true monster. O later followed Q and R were they about to have a fight.
O report this to their boss Park Mu-Bong to which his boss orders him to stop the fight to which O responds that he wouldn't do it since his duty is off unless he pays him more. Mu-Bong later came and punish the Judge, even O for disrespecting him.
Judge O has the ability to control fire and use it for combat in various ways. According to Q, he is the strongest Judge and despite having his ups and downs if he fights seriously no other Judge can defeat him. Q stated that O had won the very first G.O.H. tournament defeating himself, R, T, and K. As part of his charyeok he is usually seen manipulating fire.
Superhuman Stamina: Judge O recall fighting Changsik for Seven days and nights straight, resulting in his hair and skin burnt by Changsik's flames, exhibiting incredible stamina and Endurance.
Swordsmanship: In a fight with Jang Ho-Sik he recalls fighting Changsik. In the flashback, he's shown with medieval armor and a large broadsword, hinting a skill in swordsmanship before he became a charyeok user. He also used Dragon Slayer Sword whenever he is not directly using Red Dragon.
Dragon Slayer: Judge O's charyeok manifests in the ability to summon and command Dragons. Usually he fought the Dragons to submission first, earning the Dragon's respect. Because this ability allows O to gather sacred animals of their own free will it cannot be sealed by a Key's power ithout destroying each individual dragon first.
Red Dragon: Judge O's first Dragon. she's a large dragon with its size as close to a large multistory building. Even powerful NOX bishops such as Romario and Excaliose pay close attention to this dragon when engaging in battle.
Dragon Children: The multiple children of the Red and Black dragon, each with their own unique appearance.
- Fire Manipulation: The dragons gives O the ability to create and manipulate fire at will.
- Regeneration: The most mature dragon, Red Dragon and Black Dragon, has a very high regenerative ability.
- Polymorph: All of O's dragons have the ability to transform into a humanoid form or a hybrid between humanoid and true dragon form.
- Dragon Troops: By individually sacrificing a tooth the dragon children can summon an army of armored skeleton soldiers to fight on their behalf.
- Dragon Slayer Sword: After summoning the Dragon, O punches it and breaks one of its fangs. He uses this fang to form a blade made of flames. The flame is strong enough to shield himself from an energy blast made by priest Saturn using her National Treasure gun.
- A Nest of a Dragon: Using his dragon slayer sword Judge O creates a tornado a fire to attack his opponent.
- Protective Barrier: O can put up a protective barrier to limit damage to his surroundings.
- Breath Attack: A very powerful attack; O has stated that its damage is too great and that his own barrier cannot withstand it.
- Dragon Resurrection: A spell which O can use to resurrect the dragon, although the dragon will return as a hatchling.
- Judge O's dragon, Changsik, is a reference to the main character from an older manhwa, Dragon's Son Changsik. Youngje is known to be good friends with the author.