Not much is known of Doan's past. It is known that he was a pilot for the Principality of Zeon, piloting a MS-06 Zaku. However, during a battle, his gun had misfired and killed civilians. He was ordered to kill children, who were the children of the civilians he had accidently killed, but he could not do it. He deserted the army, took the children and took up residence on an island in the Pacific, swearing an oath to himself to protect them. Soon after, Amuro Ray would end up discovering the deserting Zeon solider. Doan and Amuro would have a short scuffle, and Doan would hide Amuro's Core Fighter. At first, Amuro viewed him as an enemy who had brainwashed the children. When a Zaku had discovered the island, Amuro was given his Core Fighter back and fought alongside Doan. As Doan explains his relation with the children, Amuro sympathizes him.

Doan had sworn never to use guns again and instead use what he called "Mobile Suit Martial Arts".

After using the Gundam to launch Doan's Zaku into the ocean, Amuro would later be picked up by White Base, leaving Doan in peace.