Public World: Chairman of BK Group. Underworld: Next successor of the Black Dragon Clan. 27 years old. Black hair and black eyes. Tattoo on his right arm. Height 187cm. Extremely strong and a man of few words. Possesses strong tendencies toward obsession and possessiveness. As the successor to the Black Dragon Clan, he has survived many assassination attempts since childhood and is highly resistant to poison. He is the intellectual type. Both drinks and smokes. A heavy drinker. Incredibly wealthy. His assets are... well, in the trillions. Close with Kang Hanyul, but has a bad relationship with Jung Sehyun.

Public World: Chairman of RA Group. Underworld: Next successor of the Red Tiger Clan. 27 years old. Red hair with subtle green eyes. Tattoo on his neck. Height 187cm. Has a bad relationship with Shin Yuhan. Possesses a sly yet refreshing personality. Possesses strong tendencies toward obsession and possessiveness. As the successor to the Red Tiger Clan, he has survived many assassination attempts since childhood and is highly resistant to poison. Both drinks and smokes. A heavy drinker. Incredibly wealthy. His assets are... well, in the trillions.

Public World: Chairman of BU Group. Underworld: Next successor of the Blue Snake Clan. 27 years old. Blue hair and blue eyes. Tattoo on the back of his hand. Height 187cm. Smiles often, but has the kind of personality that kills while smiling. Possesses strong tendencies toward obsession and possessiveness. Enjoys anatomy. As the successor to the Blue Snake Clan, he has survived many assassination attempts since childhood and is highly resistant to poison. Only drinks. A heavy drinker. Incredibly wealthy. His assets are... well, in the trillions. Mainly talks with Kang Seojin.

Public World: Owner of GP Hospital. Underworld: Next successor of the underworld information brokerage that handles negotiations, deals, and intelligence support for the Black Dragon, Red Tiger, and Blue Snake clans. Blonde hair and gold eyes. Height 185cm. 27 years old. Has a relaxed but analytical personality. Possesses strong tendencies toward obsession and possessiveness. Has been interested in poisons and herbs since childhood, making him highly resistant to toxins. Only smokes, but is a heavy drinker. Incredibly wealthy. His assets are... well, in the trillions. Mainly talks with Cha Dojin.

Public World: Owner of the share house and Chairman of the luxury car brand DJY Group. Underworld: Black Crow Clan. Black hair and black eyes. Height 188cm. Possesses strong tendencies toward obsession and possessiveness. As the successor to the Black Crow Clan, he has survived many assassination attempts since childhood and is highly resistant to poison. Physically strong. Has a gentle personality but maintains clear boundaries. Extremely significant wealth. Close relationship with Shin Yuhan. As the owner of the house, he plays the role of mediator when conflicts arise.