A thousand years ago, vile creatures arose from the Earth known as Orgs lived only for destruction. With the help of the Power Animals, five mighty warirors known as the ancient Gao Warriors were able to defeat the Org's leader, Hyakkimaru, and seal the Orgs. The shaman priestess Tetomu remained on the floating island of Animarium, in a deep sleep, along with five totem Power Animals, waiting for the day when they are once again needed. In the time that has passed, pollution has weakened the Earth, allowing the Orgs to slowly break free of their prisons. Tetomu was activated, and the five Power Animals began choosing champions who would defend the Earth as the Gaoranger. The mission of the Gaoranger grew increasingly dangerous as the Highness Org Shuten would anything to take over the world.
Throughout their adventures and during times of need, the Gaorangers would uncover the lost Power Animals. The Highness Org Ura opened a tomb in which Duke Org Loki was imprisoned by the five Gao Warriors. Loki sought revenge by destroying their successors - the Gaorangers. He defeated them time and time again, wearing them down until the day he would actually destroy them. The Gaorangers eventually discovered that Loki was actually Shirogane, the sixth Gao Warrior who became cursed by a wolf mask he put on to gain enough power to destroy Hyakkimaru 1,000 years ago. The Rangers broke the curse, and restored Shirogane to normal. Shirogane's three Power Animals granted him the G-Brace Phone, which he uses to become GaoSilver. Shirogane doesn't join the team, feeling guilty about his misdeeds, but helps the team out when they need it.
GaoGod, which was defeated by Hyakkimaru, returned to remind Shirogane of who he really was and when GaoFalcon came into the Gaoranger's possession after a trial in the afterlife, he took the form of a young boy named Futaro. He did not remember his true form but when he did, he was convinced that humanity didn't deserve the Power Animal's help because humans are wasteful creatures and only pollute the Earth. So he took away the Power Animals. The Gaorangers eventually proved themselves by showing their will to protect the Earth even without powers. He returned the Power Animals and left the duty to protect the Earth in the hands of the Gaorangers. The three Highness Orgs Shuten, Ura, and Ratesu were resurrected and then merged into Senki, fulfilling the prophecy of the "Last Org Advent". He was destroyed in the final battle by the one hundred Power Animals, who had emerged to help the Gaorangers who were then rendered to powerless. Tetomu took the Rangers' G-Phones back and stayed on the Animarium, while the Gaoranger returned to normal lives.