ULTRAMAN SAGA opens with a powerful apocalyptic vision of Tokyo, buildings destroyed and the city seemingly devoid of life. We are soon introduced to the Earth Defense Force (EDF), Team U, played by members of the female idol group AKB48. They and a group of young children are the last survivors on planet Earth.
In another universe, Ultraman Zero receives a distress call and proceeds toward the Earth in aid. From yet another universe, a young defense team pilot named Taiga is trapped in the ship of an invading alien force, who quickly disappear to another dimension.
Taiga soon finds himself in the apocalyptic version of Tokyo, as Ultraman Zero battles a huge fleet of alien spaceships. As Taiga notices a crashing ship heading straight towards a young boy, he pilots his ship directly into its path in an act of self-sacrifice. Witnessing his brave actions, Ultraman Zero rescues Taiga and joins with him.
Taiga soon encounters Ultraman Cosmos and his human host Musashi, along with Team U and the children. It is now up to Taiga and Musashi to protect the survivors. However, Taiga is not so happy to be joined with Ultraman Zero, and has no intention of fighting…