Kieron is a ruthless leader who takes pleasure in inflicting violence upon others. Perverted, obsessive, and materialistic, the head of the Mt. Kaou bandits controls his minions through fear and intimidation. In reality, he is spineless and his cowardliness shows whenever he is faced with powerful opposition.
Despite this, he held a soft spot for his little sister, Reirei. Often accommodating his behavior to fit her wishes, he had an obsessive attachment towards the last surviving member of his family.
- "So, where should I start? An ear? A finger? Or..."
- —Kieron, Genro Den Chapter 3
Tasuki and Kouji first encountered their perverted foe on a mission to steal his treasure. Unfortunately, Tasuki was a little too boastful about their quest in Souun and the two fell into the Kaou bandit's trap.
When it came time for Kieron to choose who would be tortured first, Tasuki was hauled away into his golden chamber where he was tied to a bed and cut with a dagger. But before Kieron could deliver the killing blow, he was reminded that he needed to decapitate his second in command because he was looking at his sister. The bandits tried to coerce Tasuki into becoming Kieron's lover so his life could be spared but he refused. Then, Reirei entered and freed Tasuki, scolding her brother for his disgusting behavior. Kieron backed down and allowed her to take the bandit back to his cell.
Kieron appeared again during the battle against the Reikaku bandits and promptly lost. Reirei pleaded for Hakurou to spare her brother's life and he retreated with his army back to Mt. Kaou. But Osugi, who funded the battle, allowed him to seek refuge in his palace in Souun. It was there where he witnessed his sister give her life to keep the Tessen out of the hands of Dokoro.