In
Okinawa, an
Azumi priestess has a vision of a city being destroyed by a giant monster. Masahiko Shimizu discovers space titanium while
spelunking and takes it to Professor Miyajima for examination. An excavation led by Masahiko's brother Keisuke uncovers a chamber filled with ancient artifacts and a mural bearing an ominous prophecy: "
When a black mountain appears above the clouds, a huge monster will arise and try to destroy the world; but when the red moon sets and the sun rises in the west, two monsters shall appear to save the people." Keisuke is joined by archaeologist Saeko Kaneshiro, who translates the prophecy and takes a statue bearing the likeness of Okinawa's guardian monster King Caesar to study. Two men stalk them, one claiming to be a reporter while the other attempts to steal the statue. Following the appearance of a black cloud resembling a mountain,
a Godzilla imposter emerges from
Mount Fuji and begins a destructive rampage.
Godzilla's ally,
Anguirus, confronts the imposter, only to be injured and forced to retreat. Keisuke arrives shortly after to check on Masahiko and Miyajima. As the Godzilla imposter's rampage continues, the real Godzilla confronts the imposter, revealed to be
Mechagodzilla, a massive mecha with advanced weaponry made of space titanium. Both monsters injure each other and retreat. Keisuke and Saeko take the statue back to the temple, but are confronted by the thief once again. During the fight, the skin on half of the stranger's face melts away, revealing an ape-like alien from the Third Planet of the Black Hole called Simeon. The Simeon intruder attempts to kill Keisuke, but an unseen gunman kills him before Keisuke and Saeko catch a brief glimpse of the reporter. Godzilla arrives on Monster Island during a thunderstorm and is struck by lightning multiple times, reinvigorating it. Masahiko, Miyajima and his daughter Ikuko explore the cave where the space titanium was found, but are captured by Simeons, who plan to use Mechagodzilla to conquer Earth. Their commander, Kuronuma, forces Miyajima to repair the mecha. While Saeko checks into a hotel and guards the statue, Keisuke leaves to meet Masahiko at the caves, only to encounter the reporter, who reveals himself as Nanbara, an
Interpol agent who has been tracking the Simeons. After Nanbara and Keisuke infiltrate Simeon base and free the prisoners, Keisuke and Ikuko leave to pick up Saeko and the statue while Miyajima, Nanbara, and Masahiko stay behind, only to be recaptured by Kuronuma. The next morning, a
lunar eclipse results in a red moon and a mirage of the sun rising in the west. Seeing this, the team realizes they have to awaken Caesar. They meet with the priestess and her grandfather and place the statue in the temple, revealing Caesar's resting place. As Kuronuma dispatches Mechagodzilla, the priestess sings to awaken Caesar and Godzilla arrives. The two monsters join forces to fight Mechagodzilla. When the mecha tries to escape, Godzilla creates an electromagnetic field to attract Mechagodzilla before tearing off its head, destroying Mechagodzilla. While the Simeons are distracted, Nanbara and the others free themselves, kill their captors, and sabotage the base, fleeing as it explodes. With the enemy defeated, Godzilla heads out to the ocean and Caesar returns to his resting place while the humans rejoice. ==Cast==