He is voiced by Kenyu Horiuchi in the Japanese version of the anime, and by Jarrod Greene in the English version of the anime.
Anson is first seen during his encounter with Second Lieutenant Tanya Degurechaff in her first combat mission in Norden. Anson is a loyal soldier who cares a lot for his country, comrades and family. Which is why losing half of her squadron to Tanya in their first encounter hit him really hard and the second time Tanya and her first squadron not only annihilate the majority of his wing, but also delivering a fatal blow to his country that bring their downfall. He challenges Tanya to a duel and ends up losing, but is put in a coma afterwards.
He later returns for revenge against Tanya after his previous defeat in Orse Fjord and praises to God to give him the power kill to Tanya and wipe out the Empire.
In the final battle, Anson leads his unit to fight against Tanya and her battalion. Anson takes out most of the battalion and then battles Tanya to the death.
Despite being evenly matched, Tanya ends up victorious and shoots Anson to death. But God ends up possessing his dead corpse and tries to blow himself up to take Tanya down with him, but failed.
Anson Sioux was a very loyal and religious man who was undyingly devoted to his country and people. He seems to take his job seriously as he obsessed of keeping his country safe and trying to destroy the enemy completely. Despite his serious and workaholic nature, Anson is a very loving and caring father to his only daughter Mary and he will always be there for his family during his spare time.
However, after being defeated by Tanya in the battle in Orse Fjord, Anson recovers and becomes obsessed of wanting revenge on Tanya and destroying the Empire for good. Anson believes he is God's most favourite prayer and saviour and will do whatever it takes to achieve his goals.