An ancient guardian, Mothra saved the Earth
in times past from the monster Gigan. The two
monsters battled thousands of years ago over the
fate of Earth, and Mothra ended up being victorious
over her cybernetic foe. Several millennia passed,
and the mummified remains of the cyborg kaiju
ended up displayed in an EDF stronghold for further
investigation. While confined, the creature is
studied by a team of scientists. Among them is
Paleontologist Hachiro Jinguji, who makes the
startling discovery that the creature, despite
hosting advance technology, is in fact 12,000
years old. A sudden voice chimes in to confirm
this, as the interior of the EDF lab appears to
melt away into a cave. Before the group, that
includes Jinguji and Biologist Miyuki Otonashi,
two tiny fairies, known as Shobijin, are spotted
lying on a small pedestal. The Shobijin explain
that Gigan did arrive on Earth thousands of years
ago and was fought into submission by Mothra.
The fairies then reassure the group that Mothra
will retain its role as the Earth's guardian,
before the cave dissipates to reveal the interior
of the EDF lab again.
Later, after the Xiliens have initiated a series
of attacks, Mothra answers the Earth's plea for
help and arrives in Tokyo ready to fight. Once
there, Mothra attacks the Xilien's latest kaiju,
Monster X, who was battling Godzilla. However,
the Xilien leader, spotting Mothra's descent into
Tokyo, dispatches a repaired Gigan to do battle
with its ancient foe. The two kaiju fight fiercely,
slamming their bodies into one another in mid-air,
until Gigan gains the upper hand by cutting Mothra's
wing with his new chainsaw hands. With Mothra
apparently in defeat, Gigan turns his attention
to Godzilla, and begins slashing at the monster
with his new hands, as Monster X holds the nuclear
leviathan in place. The pair's advantage is short
lived, however, as Mothra comes flying back into
the battle, striking down both Monster X and Gigan
simultaneously with her wings. Gigan directs his
efforts back at Mothra, utilizing more of his
upgraded arsenal as he unleashes two, razor like,
discs at the winged monster. Gigan's attack proves
futile, however, as Mothra effortlessly dodges
the two discs. Gigan continues the assault, though,
and lets loose with a discharge of his shotgun
like laser beam, which ignites his ancient foe
into a smoldering fireball. Gigan, pleased with
his success, turns his back to the downed moth.
However, the cybernetic kaiju made a fatal miscalculation
as the two razor discs, malfunctioning due to
Mothra's scales, boomeranged back at the kaiju,
decapitating Gigan. Then, out of the smoke and
flames, a burning Mothra ascended at her foe in
her dying breath, colliding with the robotic kaiju
and causing an explosion that destroyed the cyborg
for good.