Soo-Won

Soo-Won is a tall young man with soft, gentle features, similar to his mother, Yeon-Hee, and his father, Yoo-Hon, in height. He has sea-green-blue eyes and white skin. His light-blond hair, which reaches just above his shoulders, is usually tied in a ponytail with a gold decoration (in the manga, it was a small ribbon). He is 18 years old and his height is 185 cm.

As a child, Su-Won wore his hair loose and shoulder-length. Yona thought he was "cute as a girl," but as he grew older, his features became more masculine while still retaining some softness. Su-Won's subjects find him attractive.

In the anime, Soo-Won wears a simple white robe, belted with a purple sash, with a purple hem. Throughout the manga, Soo-Won wears upper-class clothing typical of nobility, including a yellow cape worn by kings.

Soo-Won is a complex character. Most of the time, he acts calm and cheerful. He has a lot of emotional strength and maturity, and was even able to remain calm when his father died at the age of 9, unlike any other adult in the room. He can adapt to any situation. He acts friendly towards those he likes, but underneath his smiling facade, Soo-Won is a very calculating person. He has keen observation skills that help him see people's true intentions. He pretends to be naive and carefree if it serves his purposes. Not only is this a genuine part of his personality, but it is also a tactic he uses to make his enemies underestimate him and distract them. He trusts no one, believing that no one in the world is selfless, including himself.

From an early age, he was extremely outgoing and curious, often going out of his way to gain new experiences and learn new things. He is also not one to try to live on his own. Once he gets involved in something, he is very proactive, and usually has a strong belief that he will achieve his goals together with the people around him.

However, despite all his sociability, he tends to be secretive in such delicate matters as his personal life and past.

Soo-Won is very goal-oriented and ambitious, to the point that he will even defy the will of Heaven if necessary. Just as his father, Yoo-Hong, disliked anything related to the divine, Soo-Won rejects the divine will and emphasizes throughout the series that he only cares about the "strength of the people." He has a deep love and pride for Kouka, and makes it his goal to restore its greatness and protect it from foreign invaders, especially the formidable Kai Empire.

Su-Won is skilled with a sword and other weapons thanks to his sword master and later bodyguard Hyu-Ri. Son Mundeok trained him in archery and spearmanship at an early age, much like Haku. This is confirmed in the anime when he demonstrates amazing abilities in a mock fight against Gun-Tae, a general of the Earth Clan known to be one of the most powerful generals. Soo-Won also demonstrates great political competence in dealing with the Five Generals, as well as mastery of strategy, as shown in the mock battle. Politics is his favorite field, and he demonstrates amazing people skills; however, this does not mean that he is not a great warrior himself. Although he was shown to not be as strong as Haku early in the series, he has shown to be at least close to his strength. Soo-Won is a highly intelligent, cunning, and resourceful individual; these traits have made him one of the best strategists, if not the best, shown in the series so far. One example of his abilities is his horses' tiger-like attire, which he used to scare his enemies. This tactic gave his men enough time to attack before the enemy could react. His intelligence and charisma, as well as his martial prowess, were enough to gain the support of four of the five Clans (the Wind Clan being the only exception due to their loyalty to Haku) and solidify his power as the ruler of the kingdom.

Su-Won was born in Hiryuu Castle to General Yu-Hon and Lady Yeon-Hee, and lived there for about 8 years of his life. After his mother had to move to a separate residence for treatment, he joined his father and visited Hiryuu Castle during Clan Gatherings, and often spent time playing with his close childhood friends, Yona and Haku. His relationships with his friends made him happy, and he dreamed of them remaining friends forever. However, this dream became impossible when he was forced to choose between his friends and revenge and usurpation of the throne.

When Soo-Won was 9 years old, his father was killed by Emperor Il while they were on a long horseback ride together, though the murder was passed off as an accident. Since then, Soo-Won harbored a secret hatred towards the emperor and quietly plotted revenge so that he could become king himself and fulfill his father's dying wish to restore Kouka as a world superpower. Knowing that this plan would eventually separate him, Yona, and Haku, he kept quiet about his plans and continued to live as if nothing had changed. At some point, Emperor Il revealed to him that Yona was the reincarnation of King Hiryuu and was different from him. It is later revealed that King Il had always been hostile to Soo-Won, even when he was a small child. When Yona was first born, Soo-Won approached her to greet her, but King Il did not allow him to get close and scared him away, expressing his dislike. Another time, when Su-Won and Yona were playing and were about to enter the Hiryuu Mausoleum together, King Il said that the mausoleum was not the place for him. On the night that Su-Won avenged his father, King Il told him that he would never become the Red Dragon King, and that Yona, the rightful heir, would lead him to his death.