The
Shobijin visit the elderly
Shinichi Chujo, his scientist nephew Yoshito, and his grandson Shun to warn them that
Godzilla continues returning to Japan because the
Japanese government used the
first Godzilla's skeleton in the cyborg
MFS-3 Kiryu's construction. If the government returns the skeleton to the ocean,
Mothra, the descendant of the first Mothra who attacked Japan forty-three years ago, will take Kiryu's place in defending Japan. As Kiryu undergoes repair and modifications, the Kiryu squadron is sent to the
United States for further training, with Kyosuke Akiba taking Akane Yashiro's place should Godzilla return while she is away. Due to the first Mothra's attack,
Japanese prime minister Hayato Igarashi denies Chujo's request, but agrees to discontinue the Kiryu project once the cyborg exterminates Godzilla. Sometime later, Godzilla resurfaces to attack Tokyo despite his injuries sustained since the last battle with Kiryu. Chujo and Shun summon Mothra to battle Godzilla. With the repairs finished, the government deploys Kiryu, but Godzilla knocks both it and Mothra out, injuring Chujo and Shun during the fray. Meanwhile on Himago Island, the uncharted volcanic island in
Ogasawara island chain, twin Mothra
larvae hatch from their egg and rush to help their mother. As Yoshito, with help from the Shobijin, uses a maintenance hatch to enter and repair Kiryu from its internal backup cockpit, the Japan Xenomorph Self-Defense Forces (JXSDF) and larvae try to hold Godzilla off, but the injured Mothra sacrifices herself to protect the latter from Godzilla's atomic breath while a separate attack warps Kiryu's maintenance hatch, trapping Yoshito inside. Nonetheless, he completes the repairs, allowing Kiryu to wound Godzilla before its spirit is reawakened by Godzilla's roar. After the larvae bind Godzilla in a silk cocoon, Akiba is ordered to kill Godzilla per Yoshito and the Shobijin's request. However, Kiryu lifts Godzilla and uses its boosters to carry them both out to sea. Akiba's fellow pilot, Azusa Kisaragi, blasts the hatch open. Kiryu turns over to let Yoshito escape before it plunges into the ocean and drifts into an underwater trench with Godzilla. As Japan celebrates their victory, Yoshito salutes Kiryu while the larvae return to Infant Island with the Shobijin. In a
post-credits scene, an undisclosed laboratory is shown with canisters containing the
DNA of numerous monsters. ==Cast==