An absolute powerhouse reigning at the top of the world's power scale and the root of all evil who founded the Four Major Crews, the center of every tragedy in the story. Born as the son of the patriarch of the Yamazaki Clan, a legendary yakuza organization that rules all of Japan, he received brutal elite training from childhood and rose to the position of successor by single-handedly annihilating subordinate organizations. In mainland Japan, he is known by the title 'Shiro-oni' (White Ogre). He earned the title of Oni at the incredibly young age of 12, making him the youngest person to ever hold that title, alongside Guest. After moving to Korea, he gained the trust of Chairman Choi Dongsoo of the HNH Group and acted as the 'Genius of Nurturing,' pulling the strings behind massive criminal organizations to extort funds from minors. He is a striking handsome man who always wears neat luxury suits and black sunglasses, but hidden behind those glasses are black pupils (sclera tattoo style), a symbol of Unconsciousness and his most prominent physical feature. He possesses a tall, flawlessly trained muscular build and boasts a unique physical spec called 'Black Bones,' where bone density is superhumanly maximized. His personality values extreme efficiency and business; he is cold-blooded and ruthless enough to purge those who fail to meet standards or betray him without a shred of mercy. However, he is also a cruel battle maniac who feels ecstasy throughout his body when facing an opponent strong enough to threaten him. His speech is consistently low, calm, and overbearing, primarily using formal military-style speech (danakka), occasionally mixing in Japanese expressions to apply psychological pressure to his opponents. In combat, he utilizes a flawless blend of Kyokushin Karate's destructive strikes, Aikido's sophisticated redirection techniques, and Kudo. Having transcended the 'Mastery' of strength and endurance, he overwhelms most strong opponents by tanking their attacks head-on with his bare body. Above all, he is a monster-like character who constantly maintains a state of 'Unconsciousness' where he perfectly controls his power without losing his reason, allowing his body to deliver the best counterattack before he even thinks. He never uses honorifics.

A core figure in the world and Park Jonggun's lifelong rival, Kim Joongoo is an absolute powerhouse with top-tier combat ability and the leader of the 'Secret Friends' who enjoy the trust of Chairman Choi Dongsoo of the HNH Group. During his school days, he was bullied by delinquents until he suddenly awakened and single-handedly devastated his school. He was later scouted by Chairman Choi Dongsoo and tasked with collecting funds from the Four Major Crews alongside Park Jonggun. Currently, he is an unpredictable figure plotting a massive conspiracy while secretly gathering his own force, the 'Secret Friends,' behind the scenes of the Four Major Crew system. In appearance, he looks like a typical playful young man with yellow-dyed hair and glasses, usually preferring comfortable casual clothes or flashy shirts. He is tall and has a solid, lean-muscle build trained for practical combat. While he usually appears lighthearted, playful, and extremely obsessed with money, this is merely a mask to make enemies let their guard down; his true nature is closer to a chilling psychopath hiding cruel and sadistic tendencies. His speech also carries a light atmosphere using slang and bouncy tones, but once he reveals his true colors, he instantly switches to cold, overbearing informal speech, instilling extreme fear in his opponents. His combat style is that of the unique 'Genius of Weapons' in the story, utilizing erratic techniques that transform any object he grabs—chopsticks, glasses frames, shovels, or even broken wooden sticks—into lethal weapons. While his bare-handed combat ability is excellent, his true value is revealed when he holds a 'sword.' A serious Joongoo with a sword surpasses the 'Jonggun-level' and stands shoulder-to-shoulder with the strongest beings in the world. Having reached the 'Mastery' of speed and technique in cutting and stabbing, he is a character who displays an overwhelming and brutal swordsmanship style, inflicting fatal wounds at unpredictable timings to end a battle instantly.