Ki-Ja is the first of the Four Dragon Warriors to join Yona on her journey. He is twenty years old and serves as the bearer of the White Dragon's power. His entire life was shaped by the legend of the dragons, as he was born and raised in the secluded White Dragon Village, a community that venerates the dragon bloodline. From childhood, he was strictly raised to fulfill the role of the White Dragon warrior, a duty reinforced by the village elders and his grandmother, who prepared him for the eventual arrival of a master foretold by prophecy. This isolated upbringing left him sheltered from the wider world and lacking in common everyday sense.

Ki-Ja has an earnest, sincere, and deeply prideful personality. He carries himself with an aristocratic formality and possesses a strong sense of duty that often leads him to be the most well-behaved and polite member of the group. However, this seriousness is balanced by comical and endearing flaws. Ki-Ja harbors a notable fear of insects, which stands in stark contrast to his formidable combat abilities. His personality is also marked by a competitive streak, especially in his ongoing rivalry with Hak, whom he sees as a rival for Yona's attention. This rivalry often manifests in humorous ways, such as when Ki-Ja attempted to bribe Hak to leave Yona's side.

Ki-Ja’s primary motivation is his unwavering loyalty to Yona, whom he recognizes as his destined master due to her crimson hair, a sign of the legendary Crimson Dragon King. Initially, his devotion is rooted in the sacred prophecy he was taught from birth, compelling him to obey his master without question. This sense of destiny gives him the initial drive to leave his isolated village and pledge his absolute allegiance to Yona, promising to follow and protect her at all costs.

In the story, Ki-Ja serves as a powerful protector and one of Yona's key warriors. As the first dragon to join the party, his enthusiastic acceptance of Yona and the prophecy helps set a precedent for the other dragons who are found later. His presence also creates significant group dynamics. His relationship with Hak is defined by a fierce and often comedic rivalry, with Hak frequently mocking Ki-Ja by calling him a white snake. While Ki-Ja can be annoyed by Hak's demeanor, the two develop a mutual respect as fellow fighters dedicated to Yona's safety. His relationship with Yun is more cooperative, with Yun often using his practical intelligence to guide Ki-Ja, whose sheltered upbringing leaves him naive about the world.

Throughout the series, Ki-Ja undergoes significant character development. He begins as a man whose entire identity is tied to the prophecy and his sacred duty as a weapon for a destined master. Living in an isolated village, he felt trapped by his role, bound to wait for a master who might never arrive and pressured to produce offspring to continue the dragon bloodline. However, as he travels with Yona and witnesses her courage, determination, and selflessness, his loyalty evolves from an inherited obligation to a deeply personal choice. He transitions from serving an idea to protecting the person Yona has become. By the end of the main story, after the dragon gods disappear and all the warriors lose their powers, Ki-Ja becomes an ordinary person and chooses his own path in life, finally free from the burden of his inherited destiny.

Ki-Ja's notable ability is the power of the White Dragon, which is concentrated in his right hand. When unleashed, his hand transforms into a massive, powerful dragon claw that possesses strength far beyond that of a normal human. This claw can deliver devastating blows capable of overwhelming enemies and even moving obstacles like large boulders. In order to not draw attention or cause harm accidentally, he typically keeps his dragon hand wrapped in bandages when it is not in use.