King Kou Retsu had a long goatee with a thick mustache. He is seen with regal court robes that look black in color.
Kou Retsu had a dominating presence and an angry visage to the point where his subjects in court sweat in fear of him. He had a habit of cracking walnuts when angry and has no qualm with killing those who fail him. He is also wise as he is willing to secretly adopt Shun Shin Kun's child as his heir due to being unable to sired a child, in order to prevent his younger brother a deviant from taking the throne, willing to allow the royal bloodline of Chu to end rather letting his country be ruined in hands of his younger brother.
It is assumed that he was the oldest son of the previous Chu king and took the throne after his father's death.
Upon news of the death of Kan Mei and Rin Bu Kun, Kou Retsu was angered at this failure in the coalition war and orders the death of those responsible when they return. Wondering if he was too stingy in his contribution to the coalition, he asks Ren Pa for his opinion and considers sending out one of his Great Generals. Ren Pa tells him that Kou En will not be able to reform the Chu army and points out that the war is not over as Ri Boku has yet to make a move on the battlefield.
He passed away shortly before Shun Shin Kun was assassinated.
It is assumed that he had great political power in the state and can make key decisions for his people. He was also able to smash walnuts with his bare hands.