Dufaux (Dufort in the English version) is Zeon's bookkeeper. He's very silent and reserved, almost to the point of having no emotion, and he has psychic abilities.
Dufaux, his life was a total mystery, until he told his story to Kiyomaro and Gash near the end of the Faudo saga. The story was quite different in the manga than in the anime.
Anime: According to Dufaux's story, he had powerful psychic abilities. For this reason, he was confined to an asylum, experimented on and possibly abused throughout nearly his entire life. He vowed to destroy humanity for what they did to him in the past. That hatred is what took Zeon's attention and came to release Dufaux from the asylum.
Manga: Dufaux's tale has also been revealed as slightly different in the manga: he had been sold to a mad scientist by his own mother for a price of ten thousand dollars. The scientist subsequently performed mental and emotional experiments throughout his childhood, culminating with the passage of his ultimate test leading both to his own freedom and the destruction of the lab, revealed to be located at the North Pole. Forced to wander in the snow and cold for his own survival, he eventually encountered Zeon, who took him and made him his bookkeeper.
The manga also revealed that Dufaux possesses an ability known as "Answer Talker", which allows the user to understand how any attack is applied and how to defend against it. This awakens whenever a human "dies and then returns to life", such as Kiyomaro himself in the manga after he is killed by the mamono Riou and then subsequently revived within Faudo tower.
Although Dufaux's fate is not determined at the end of the anime outside the escape from Faudo, he ends up wandering off in the manga after Zeon goes back, trying to find a purpose after being used for so long. Eventually he uses his "Answer Talker" abilities to help others whether he wants to or not, finally appreciating everything both Zeon and Gash had done for him. He later returns to help Kiyomaro to develop and control his Answer Talker ability so that he could use it anytime in preparation for the fight against Clear Note. In conjunction with his Answer Talker, Dufaux felt different places in each of their heads of the mamono in order to determine the training style each needs during the ten month lull while Clear recuperates within Goomu's dimension.
In the original Japanese version, Dufaux is voiced by Hikaru Midorikawa.
In the VIZ Media dub, Dufort is voiced by Dave Wittenberg.
(Source : Wikipedia)