A Giant of Light who merged with Jonan University student and genius scientist Gamu Takayama. When he transforms, he is bathed in the red light of the Earth. Gaia was born from the will of the Earth itself to protect it from the invasions led by the Radical Destruction Bringer.
When Gamu runs an experiment to try and figure out how to save the Earth from destruction he is taken to a particle acceleration realm at the center of the Earth where Gaia reveals himself to Gamu. Later when the Space Combat Beast C.O.V attacks, Gaia responds to Gamu’s desire for the strength to stop it and bonds with him.
Ultraman Gaia’s special attacks are his Photon Edge, where Gaia focuses energy into his head to make a blade of light and attacks the enemy with it like a whip, and his Quantum Stream, a beam he fires by crossing his left and right arms together.
At first, he sees all monsters as dangerous to human existence, but over time he comes to realize that monsters born on Earth as fellow terrestrial lifeforms. From then he also protects the monsters of Earth and tries to find ways for monsters and humans to coexist.
In the final battle against the Radical Destruction Bringer, Ultraman Gaia, Ultraman Agul, and the monsters of Earth come together to fight back, and together they defeated the Radical Destruction Angel Zog and restore peace to the Earth.