JSDF pilot Akane has a fateful encounter when a new Godzilla emerges in Tateyama. As a countermeasure, a cyborg named Kiryu is constructed from the remains of the original. The machine is discovered to harbor the restless soul of the original monster as Akane must learn to find value in her own life as well.

An Okinawan prophecy that foretells the destruction of the Earth is seeming fulfilled when Godzilla emerges to return to his destructive roots. But not all is what it seems after Godzilla breaks his ally Anguirus's jaw. Matters are further complicated when a second Godzilla emerges, revealing the doppelgänger as a mechanical weapon.

The U.N.G.C.C. (United Nations Godzilla Countermeasure Center) recovers the remains of Mecha-King Ghidorah and construct Mechagodzilla as a countermeasure against Godzilla. Meanwhile, a giant egg is discovered along with a new monster called Rodan. The egg is soon found to be none other than an infant Godzillasaurus.

Mothra and her fairies return to Japan to warn mankind that they must return Kiryu to the sea, for the dead must not be disturbed. However Godzilla has survived to menace Japan leaving Kiryu as the nation's only defense.