|Japanese Name||Kai (カイ)|
|Voice Actor||Kentarō Itō|
|Relationships||Merriot (Adoptive sister)|
- "King of Caerleon, which is known as the "Magic Kingdom". A young man so gentle that he may give the impression that he is a weak king, but he has profound wisdom and passion in his heart. He is also known as the Silent Wise King."
Cai is compassionate, a good listener, and a diplomat by nature. In certain situations, he is shown to think things through and choose the best possible course of action. When Merriot and Cierra decided to give him jewelry as gifts, he respectfully declined them since he thought about what his people would think of him. Since Caerleon is a poor country, people would not want their king to waste his money on jewelry. He decides to tell them that they should exchange gifts with each other instead. He is also very humble. When Vaynard said that Cai was the smartest man on the continent, he replied that he is just a man who wants happiness. He also said that he would rather not fight if he didn't have to, but he won't run because he has people he needs to protect.
Cai is a thin man with black hair and blue-black eyes. He dresses in simple clothes of green and yellow, complete with a scholar's cap and a light brown cape that fastens over one shoulder. He carries a book with him that he uses to cast spells and attack enemies in battle.