Gen Kai (元魁) is the father of Atsuyu and previous Governor of Gen Province. Gen Kai was thought to have retired in the Inner Palace due to illness but in reality Atsuyu had him imprisoned without food nor drink since taking the Govenor's seat. As a sennin, starvation could not kill him, so he suffered greatly. When Atsuyu is forced to show his father to the public, he uses an insane man whose tongue he severed to impersonate his father.
When he is held hostage in Gen Province, Enki initially finds a prisoner chained to the floor of a prison cell and under an enchantment that renders him unintelligible; Enki assumes the insane man is Gen Kai. However, as Enki moves further into the dungeons of the provincial palace, he finds the true Gen Kai and realizes the prisoner is an imposter. Gen Kai explicitly reveals Atsuyu's true nature - a man who is so sure of himself, he cannot stand the thought of failure and the humiliation that follows it.