Godzilla Minus Zero introduces another formidable kaiju in Ghidorah. Introduced with just one head, the creature originates from a mysterious white substance that crash-landed in Japan sometime between the events of Godzilla Minus One and this sequel. Scientists discover that the substance can absorb the DNA and physical traits of nearby animals, and name the monster "Ghidorah" by combining "chimaera" and "hydra."
Following Ghidorah's attack on Ginza, naval weapons engineer Kenji Noda (Hidetaka Yoshioka) and meteorologist Makoto Aoyama (Masami Nagasawa) devise a plan to destroy it. Their first attempt involves an American fuel-air bomb, but Ghidorah survives. Next, a bomber attaches a lightning rod to the monster's back, attracting lightning bolts and grounding it. However, instead of killing Ghidorah, this only makes it more powerful, transforming the beast into a golden-skinned, three-headed monster with two tails and a terrifying gravity beam.
This transformation seemingly awakens Godzilla, who regenerates and resurfaces offshore, larger and more aggressive than before (the movie never explains exactly why Ghidorah's evolution causes Godzilla to reemerge). Elsewhere, we learn how Noriko Shikishima (Minami Hamabe) survived Godzilla's attack on Ginza in Godzilla Minus One. Exposure to the monster infected her with its cells, known as G-cells, giving her unusual resilience. Other infected individuals developed horns and scales before dying from their mutations, but Noriko survived.
With two kaiju threatening Japan, Noda and Professor Kanji Murakami (Min Tanaka) decide their best bet is to make the monsters fight. They use the Resonance Wave, a device that exploits the shared DNA between Noriko and Godzilla, to lure the latter towards Ginza. Ghidorah, meanwhile, is drawn there by electrical generators and the storm systems it typically follows.
Godzilla and Ghidorah eventually clash, with the former severing one of his opponent's heads. However, the detached head latches onto Godzilla's arm and tears it off. While Godzilla regenerates, Ghidorah gains the upper hand by using its gravity beam to bring buildings crashing down on him. Noda attempts to repair damaged fuel lines meant to help fell the beast but is killed when Ghidorah strikes his vehicle.
The Resonance Wave is activated again to awaken Godzilla, while Ghidorah reattaches its missing head. However, that appendage has absorbed G-cells, giving Ghidorah Godzilla's scales, dorsal spines and heat ray (and making it look a little more Godzilla-like). The monsters prepare to unleash their respective energy beams, but Ghidorah struggles to control its newfound abilities. Godzilla takes advantage, blasting his opponent and finally killing the kaiju.
Having lost his family when America dropped an atomic bomb on Hiroshima, Murakami initially intends to use Noriko's G-cells and the Resonance Wave to lure Godzilla to New York City. He wants the monster to devastate American civilians, with promotional footage showing Godzilla approaching the Statue of Liberty depicting what he hopes to accomplish (yes, Godzilla never actually heads stateside).
Noda eventually changes Murakami's perspective by warning him that the technology could be used to weaponise Godzilla for countless sinister purposes. Those concerns prove justified when American forces arrive in Japan following the battle and allow Godzilla to return to the ocean, intending to preserve him for future use. Murakami destroys his research and attempts to flee, but is apprehended by U.S. Forces.
Fearing the Americans will experiment on Noriko and weaponise her G-cells, she and Shikishima decide to go into hiding. Their initial plan involves leaving Akiko at a local orphanage, but saying goodbye proves difficult. During their final visit, the young girl begs them not to leave, repeating "Have a safe trip," a phrase previously used to assure her that it will bring her loved ones home.
Ultimately, Shikishima and Noriko decide to keep their family together. The closing moments show Shikishima setting off on his motorcycle with Noriko and Akiko alongside him, though the trio will likely face an uncertain future together while evading the American military.
The door is left open for a potential sequel, suggesting the monster could eventually be weaponised by the Americans. With Noriko's G-cells and the Resonance Wave potentially still in play, Godzilla could yet head towards American shores, with any attempt to use the beast as a force for good bound to backfire.
Godzilla Minus Zero is now playing in theaters.