Gaia is the main villain of the first Battle Arena Toshinden fighting game, but then later became a protagonist. He and his wife Kaede used to be part of the Himitsu Kesshu organization. Although Gaia was a member of the Divine Four of the organization, someone who was to be Uranus told Gaia and his wife to quit. As Gaia and his family were driving, an unknown incident occurred when the car was hit.

Gaia and his daughter Ellis were the only survivors. He sent his daughter to Turkey as to not have Ellis involved in the hunt for the killer. Uranus brought him into the Divine Four and told him that she was the murderer. To get revenge, he held a Toshindaibukai tournament without orders until only he and Eiji Shinjo remained. Eiji had doubts on Gaia's proposition, but another Divine Four, Chaos interrupted the fight, declaring Gaia a traitor. Gaia redeemed himself years later by relieving his demon armor, and fighting on Eiji's side. By the time he saw Uranus, she was dead.