Kiryu is undergoing repair modifications after its battle with Godzilla. Prime Minister Hayato
Igarashi accepts Lead Scientist Yoshito Chujo’s choice to replace the Absolute Zero Cannon
with a powerful Tri-Maser.

The Shobijin (Mothra’s twin fairies) warn the Japanese government that Godzilla continues
returning to Japan because they used the original Godzilla’s bones in Kiryu’s design. If they
return the bones to the bottom of the sea, Mothra would gladly take Kiryu’s place in defending
Japan, but if they do not, Mothra will declare war on humanity. Soon enough, Kamoebas, a
giant mata mata turtle, is found washed ashore on a Japanese beach. It is determined by the
wounds on Kamoebas’ neck that Godzilla killed it. Godzilla and Mothra fight, but Godzilla
seems to have the upper hand. With the repairs finished just in time, Kiryu manages to even
the odds, but Godzilla manages to knock out both monsters.

Meanwhile, on Infant Island, two twin Mothra larvae hatch from Mothra’s egg, and rush to help
their mother. As Kiryu was being repaired, the larvae try to hold Godzilla off, but Mothra is
killed by Godzilla’s atomic breath while trying to save her children. Just in time, Yoshito and
the humans repair Kiryu, who stabs Godzilla’s chest with a drill, causing Godzilla to bleed.
Godzilla roars in pain, and the larvae begin to bind him up in web.