Gaia is a huge monk-like warrior, who was once an elite member of the Secret Society; a criminal organization that sponsored the Toshinden tournaments. Gaia's wife Kaede, who was once the "Uranus" of the group, was killed in a car crash and Gaia suspected that the woman who was destined to be the next Uranus was behind the crime. Determined to seek vengeance against the new Uranus, Gaia had held the first Toshinden tournament behind the back of the Secret Society in an attempt to start a rebellion. However, when Uranus learned that he had held the first tournament without the approval of the organization, she branded him a traitor and marked him for death. However, Gaia escaped and went into hiding.

One year later, Gaia had received an invitation to participate in the second tournament. He reunited with his long-lost daughter Ellis and entered the tournament with her, hoping to get revenge on Uranus. At the end of the tournament, they were successful in destroying her and the Secret Society with the other fighters. However, Gaia had then discovered that he was being targeted by the Organization, a long-time rival group of the Secret Society. He entered the tournament hosted by the Organization with Ellis, in order to help bring it down. Gaia's whereabouts after the events of Toshinden 3 is never explained, but it is likely that he may have reconciled with his daughter Ellis before his departure and he told her that he would always be there for her.