After their defeat at the hands of Godzilla Earth, Haruo Sakaki and his team meet a mysterious tribe of humans who have lived on Earth for 20,000 years, and discover a massive fortress built by Mechagodzilla, a long-lost anti-Godzilla weapon.

Godzilla: City on the Edge of Battle
As humanity struggles to reclaim the planet from Godzilla's destruction, they turn to a powerful ally: Mechagodzilla, a 20,000-year-old robotic warrior.