Three years have passed since Gamera defeated Legion, and the world is once again threatened by a sinister new menace: Hyper Gyaos that have evolved beyond their former forms. Shinobu Nakayama portrays Mayumi Nagamine, a renowned ornithologist who steps back into the fray to help the Japanese government confront this peril. Deep beneath the Pacific, where Gamera once left his fossils, researchers uncover a graveyard of those ancient guardians, hinting at forgotten histories and powers still at play. Meanwhile, shadowy figures—occultist Mito Asakura and Kurata Shinya—move with their own hidden aims; Asakura sees Gamera not as a protector, but as an evil spirit that must be confronted. (Senri Yamazaki and Toru Tezuka anchor these enigmatic figures as the story threads pull tight.)
In Shibuya, a dramatic confrontation unfolds as Hyper Gyaos materialize and clash with the veteran guardian. Gamera, a creature both awe-inspiring and devastating, engages with a ferocity that spares no one, and in the ensuing battle, the city endures unimaginable loss—twenty thousand people perish as Gamera attacks the Gyaos with little regard for civilian safety, provoking the government to order the creature’s destruction. Amidst this chaos, a teenage girl named Ayana Hirasaka—whose parents were killed by Gamera during a prior engagement with Super Gyaos in 1995—stumbles upon a sealed stone egg inside Asuka’s temple, an artifact that will change everything. The young woman’s discovery sets in motion a perilous chain of events that tests loyalties and reshapes her world.
From the egg emerges a tentacled mutant named Iris, a creature who awakens Ayana’s own impulse for vengeance and forms a bond with her through an orichalcum amulet. Ayana’s connection to Iris becomes the focal point of her quest for retribution, even as Iris itself grows and threatens to consume her. Iris’s maturation accelerates when Tatsunari Moribe—Ayana’s classmate and a friend who seeks to do the right thing—manages to free her from Iris’s cocoon using a sacred dagger, but Iris escapes into the world, leaving tragedy in its wake as he massacres half of Asuka’s population before maturing into his adult form. The rapid escalation of danger pushes the JGSDF to respond, yet Iris proves too formidable to be easily handled.
The conflict shifts toward Kyoto as Iris heads there, and Ayana is taken by Asakura and Kurata, who intend to harness the creature’s power to their own ends. A desperate chase unfolds as Iris attempts to strike down two JASDF pilots, only to be intercepted by Gamera, reigniting an aerial duel that ends with a tactical missile strike forcing both adversaries to descend. Iris escapes, with Gamera in pursuit, but the chase continues toward Kyoto Station, where Nagamine and Asagi Kusanagi—Ayako Fujitani in the role—try to salvage Ayana from the escalating catastrophe that typhoon winds also threaten to magnify.
Kurata theorizes a troubling possibility: Gamera might be humanity’s guardian, a vessel that can be charged with the collective mana of humankind. If this is true, Iris appears to have been engineered to defeat Gamera so that the Gyaos could bring humanity to its knees. Nagamine and Asagi, haunted by this mana hypothesis, cling to the belief that Gamera’s power is linked to humanity’s resilience and moral energy, even as the battle intensifies. As Iris accelerates toward Kyoto Station, a brutal clash erupts in which Iris impales Gamera’s hand, tearing through the station’s debris and killing Asakura and Kurata in the collapse.
Desperate to halt Iris, Moribe uses the sacred dagger to distract the creature; Iris, however, overwhelms Ayana and begins to absorb her. Inside Iris, Ayana experiences Iris’s memories and arouses an emergent understanding of her own hatred and bitterness as driving forces behind Iris’s deeds. In a dramatic turn, Gamera—already injured—drives his arm into Iris’s chest, severing the human-link and saving Ayana from complete absorption. Asagi rescues Nagamine from the wreckage as Iris destroys Gamera’s hand and begins to process his DNA. Iris conjures a plasma fireball, but Gamera, thrusting away his own injury, burns Iris with a fiery plasma fist and destroys him in a spectacular explosion.
Ayana lies in a coma, but Gamera’s roar awakens her, and Nagamine and Asagi stand by as they watch Moribe, who survived Iris’s assault, offer quiet support. Although Ayana remains unconscious, the crisis leaves a glimmer of hope—Gamera has saved her and may still be a guardian for humanity. In the aftermath, a swarm of Hyper Gyaos descends on Japan, intent on finishing their mission, but the military leadership finally recognizes that Gamera stands with humanity and vows to fight beside him. Asagi reflects that their psychic link to Gamera may be broken for now, but she trusts that the steadfast guardian will not waver. In a final, defiant act, Gamera roars from the center of Kyoto as the Hyper Gyaos bear down, ready to clash once more and defend the world.
(Note: Gamera is presented as a legendary force in this narrative, with the following linked performers: Gamera [Hirofumi Fukuzawa], Mayumi Nagamine [Shinobu Nakayama], Mito Asakura [Senri Yamazaki], Kurata Shinya [Toru Tezuka], Ayana Hirasaka [Ai Maeda], Asagi Kusanagi [Ayako Fujitani], Iris [Akira Ohashi], Shigeki Hinohara [Kei Horie], Shigeki’s father [Satoru Saito], Shigeki’s mother [Toshie Negishi], Tatsunari Moribe [Yūsuke Kawazu], Ayana’s father [Kunihiko Mitamura], and Ayana’s mother [Kazuko Kato].)
