Hyoga is one of 100 children bastards Mitsumasa Kido, and the only one who knew that this was his father because his mother was still alive, and she was able to tell. He lived with his mother in Kohoutek Village, Siberia (then part of the USSR).
To go meet her father for the first time, the ship bound for Japan sinks, and his mother can not save; Japan, Mitsumasa Kido for it in an orphanage and tried not to give her affection; Hyoga never told the other half-brothers the truth about his father.
Hyoga is sent to Siberia to get the Cygnus Cloth, and so it takes to try to break the ice on the ship of his mother, who is sunk; Hyoga can this goal, but that without finishing your workout. But his master, Camus, leaves of Siberia without completing his training, and only after he gives a letter that indicates where is the cloth, and sends him to use it to kill Seiya and the other saints, who violated the rules of the sanctuary to fight for their own account in the Galactic Wars. Hyoga grabs the cloth, and after seeing that they have a goal in their struggle, decides not to kill them, and this makes the sanctuary consider him a traitor, who joined the sinners.
Hyoga, in the second series movie, went to Asgard, to talk with Drbal, but, he suffers a brainwash and was named Midgard, and served Drbal. Only after Shiryu defeat Hyoga, he turns good back.