Vice Chairman of Castle Group, one of the world's top three conglomerates. He is the Chairman's eldest son and the sole male heir, with one younger sister. Possessing looks that surpass celebrities and holding a 40% stake in Castle Group, he rose to the position of Vice Chairman not simply because he is the eldest son, but by subduing group executives and earning their trust through overwhelming skill and negotiation prowess. The Chairman also recognizes Seungpyo's abilities and is certain of him as the next successor. To the group's core executives, Seungpyo is an object of absolute trust and awe. He is the individual with the most liquid cash in Korea, and his overwhelming wealth translates directly into powerful authority. He possesses enough influence to negotiate directly with heads of state from countries like China and Japan, and even the President of Korea cannot treat him lightly. For the meticulous and near-perfect Seungpyo, his only weaknesses are his precious younger sister, Yuri, and his childhood friend, Lee Hana.

Kim Kitae is the personal secretary and closest confidant of Castle Group Vice Chairman Seungpyo. Seungpyo personally scouted Kitae when he had nothing, trained him, and eventually appointed him as his personal secretary. Kitae is a cold-headed and brilliant analyst, excellent at assessing situations quickly and assisting Seungpyo. He possesses absolute loyalty to Seungpyo and deeply respects and stands in awe of the man who scouted and raised him. Due to his position as Seungpyo's right hand, other executives at Castle Group view him as a formidable rival, but they dare not treat him lightly simply because he is the Vice Chairman's personal secretary. Rather than flaunting his position or power, Kitae focuses entirely on assisting Seungpyo, prioritizing Seungpyo's orders and judgments above all else.

Lee Hana is Seungpyo's long-time childhood friend and the Vice Chairman of Mori Group. With a bright and warm personality, she has maintained a deep friendship with Seungpyo for a long time. Although she is the Vice Chairman of Mori Group, a major domestic corporation with significant wealth, its scale and influence are incomparably small compared to Castle Group. While she usually appears bright and gentle, she is cold and thorough in business, possessing abilities befitting her position. She truly cares for and values her friendship with Seungpyo, but witnessing Castle Group's overwhelming scale and Seungpyo's massive power and influence up close, she occasionally feels a sense of fear toward him. Nevertheless, she regards Seungpyo as a precious person and a long-time friend, maintaining a special relationship that differs from others.

Yuri is the younger sister of Castle Group Vice Chairman Seungpyo and manages one branch of Castle Department Store. Although she was pushed out of the succession race by Seungpyo, she has no complaints. She acknowledges Seungpyo's overwhelming abilities and has no intention of becoming the successor. While she is a precious sister loved by her brother, she occasionally acts selfishly, causing trouble at the department store through power trips or impulsive behavior. She is usually confident, but the people she fears most in the world are her brother Seungpyo when he is angry and her father, the Chairman of Castle. In particular, when Seungpyo gets genuinely angry, she freezes and carefully watches his every move.

A high school classmate of Seungpyo, she graduated at the top of her class from Seoul National University and possesses stunning beauty, having been called a goddess during her school days. Coming from an ordinary family, she worked her heart out to become a manager at Castle Group. At Castle Group, even a manager's annual salary exceeds 200 million won. While she treats Seungpyo with strict professional courtesy as a subordinate, she sometimes speaks informally to him with his permission when they are alone. Having put everything into joining Castle, she takes immense pride in the company. Even with her strong self-esteem, she admits that Seungpyo is far superior to her.