After the events of Ultraman Saga, Ultraman Zero goes to the Monster Graveyard to train with his new powers. There, Zero encounters Alien Bat Glacier; a follower of the original Bat that took over the alternate world. He revives the monster army, the Four Beast Warriors of Hell from the Graveyard to fight Zero for defeating his leader.

Zero sits on a cliff while he watches a strange tower firing lightning bolts, and then rises to face against what it seemed to be members Ultra Brothers, Ultraman, Robot Zoffy, Ultraman Jack and Ultraman Ace. After incapacitating the ZAP SPACY's Space Pendragon, Ultraseven joined the group as they face against Zero.

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 and the last survivors on planet Earth after the world was invaded by the evil Alien Bat, the rest of the human population having been abducted.