On July 17, 1966, three close friends — Daigo Madoka, Shin Asuka, and Gamu Takayama — gather at Daigo’s house to watch the very first broadcast of the Ultraman television series. This shared experience profoundly inspires them, planting seeds of dreams about doing great things in the future. During a game of softball, the trio encounters a mysterious young girl whom they invite to join their game. As they converse about their hopes and ambitions, Asuka aspires to become a professional baseball player, Daigo dreams of being an astronaut who pilots a spaceship to Ultraman’s homeworld, and Gamu hopes to become a scientist capable of building such a spaceship. Interestingly, the girl never reveals her own wish but bids farewell to Daigo before suddenly disappearing, leaving an air of mystery about her.
Fast forward 30 years, the three men have drifted apart from their childhood passions, absorbed in their everyday lives as ordinary civilians. Daigo, now a busy tour guide, rushes to work after waking late. While on his commute, he witnesses a strange mirage hovering over Yokohama that displays a vision of a devastated city under attack from giant monsters (Kaiju). In this vision, a group of eight Ultramen fighting to defend the city appear vividly. During this unsettling moment, an antagonist named Alien Nackle — a villain from The Return of Ultraman — announces that the Ultraman Mebius has been captured and threatens to destroy Earth alongside the alien Guts, an adversarial race from Ultra Seven.
The vision ends with the appearance of elderly men Shin Hayata, Dan Moroboshi, Hideki Go, and Seiji Hokuto, who transform into Ultramen right before Daigo’s eyes. As the mirage dissipates, Daigo encounters Hayata's daughter, Rena, on the boardwalk, and together they realize that the apocalyptic scene resembles Yokohama’s destruction from Daigo’s vision. While talking to Shin and Gamu, Daigo connects the names of these men with the original Ultras — Ultraman, Ultraseven, Ultraman Jack, and Ultraman Ace. The next day, Daigo has another vivid vision — this time of a fierce battle between Mebius and the monster U-Killersaurus Neo.
A strange man appears, claiming to know Daigo and professing support for him. Daigo considers the possibility that he’s perceiving a parallel universe, where he and his friends are Ultramen, protecting their worlds. He shares his theories with his friends, but they dismiss his ideas as fantasy, while Daigo is haunted by fleeting moments of the mysterious girl from his childhood, who appears briefly and vanishes. Suddenly, a dark-robed figure causes chaos by sending a truck hurtling toward children on the street. In an impressive display of heroism, Hayata, Dan, Go, and Hokuto transform into Ultramen and stop the vehicle just in time. The cloaked figure laughs maniacally and disappears, leaving a sense of foreboding.
As a tour guide, Daigo leads a group to Yokohama’s Red Brick Warehouse, where he experiences another disturbing vision of King Guesra, a monster from the very first episode of Ultraman, rising from the sea to devastate a building. The Ultraman Mebius intervenes but is quickly overwhelmed by Guesra. Daigo, recalling the original fight, urgently advises Mebius to target the monster’s weak point at its fins — a strategy that leads to Guesra’s destruction. This moment is fleeting, as Mirai Hibino — the human form of Ultraman Mebius — appears, thanking Daigo, only to suddenly revert to his usual human guise, leaving both men bewildered. Mirai admits he doesn't understand how he arrived there, frustrated that Ultramen and Kaiju are merely fictional in Daigo’s world, and tells Daigo about a girl in red shoes who instructed him to awaken seven warriors to prevent the destruction of their world.
Mirai’s attempt to connect with Hayata, Moroboshi, Go, and Hokuto results in rejection, as they don’t recognize him and accuse him of harassment. Meanwhile, King Pandon appears via a tornado, wreaking havoc across Yokohama. Mirai, transforming into Mebius, fights Pandon fiercely. The city descends into chaos: Asuka and Ryo seek shelter from a baseball stadium, and Gamu and Atsuko evacuate frightened citizens from a museum. Amid destruction, Aki — Go’s wife — helps an elderly man, but is injured by debris from Pandon’s attack. Enraged, Mebius defeats the monster with a powerful Lightning Thrasher and Mebius Shoot, saving many lives. Just as he strikes the final blow, Alien Hipporit appears, traps Mebius in a cylinder turning him into a bronze statue, and announces its destructive plans against humanity before disappearing again.
In the hospital, Aki remains unconscious after the attack while Go slips into depression. Daigo desperately pleads for Mebius’s help in summoning the other Ultras, but to no avail. Meanwhile, Rena reassures Daigo that she believes in him, but he confesses that he stayed behind in Yokohama hoping to protect her. That day, monsters King Silvergon and King Goldras emerge, causing chaos across the city. Gamu and Asuka reflect on their childhood dreams — Gamu regrets not accepting the responsibilities of being a scientist, while Asuka recalls how he was demoted to a ball boy after missing a key play, though he persisted with hope of another chance.
Rena manages to contact her boss at a radio station, pleading for permission to broadcast a message of hope. As the radio waves spread across Yokohama, the city’s residents and the three friends are inspired to believe in their dreams once more. Hayata, Dan, and Hokuto arrive to reinforce this resolve, reminding Daigo of a phrase he once told them: "As long we don't give up, Ultraman will surely come." This moment sparks a profound vision, revealing the mysterious girl’s wish: for Daigo and his friends to become Ultramen — the heroes capable of saving their world.
A radiant light surrounds Daigo, transforming him into Ultraman Tiga with the iconic Sparklence. Inspired and determined, Tiga joins the fight against the monsters alongside Ultraman Dyna and Ultraman Gaia, who have also stepped in. Despite the combined efforts of the Ultras, they are initially overwhelmed as Hipporit traps Tiga into a cylinder to turn him into a bronze statue. But with the support and belief of the crowd, Gamu and Asuka transform into Ultraman Gaia and Ultraman Dyna, freeing Tiga and uniting their powers for a final assault. They manage to obliterate the Giga Chimaira, a colossal monster resurrected from the defeated monsters by cloaked beings intent on destroying all Ultramen across universes.
Despite their victory, the cloaked beings vow to annihilate every Ultraman in all worlds, but they are ultimately defeated by the combined efforts of the Ultras. As order is restored, Go receives news that Aki has awakened and recovered. Mirai bids farewell to the team and returns to his own universe, promising to meet again one day.
Years later, Asuka has become a successful professional baseball player, praised by Gosuke Hibiki as his best player. Gamu has become a renowned scientist developing advanced technology such as anti-gravity devices. Daigo finally achieves his childhood dream of becoming an astronaut and marries Rena. Their daughter, Hikari, grows up to meet the mysterious girl in red shoes from childhood, symbolizing hope and continuing their journey.
Sometime later, a giant spaceship, once a monument, is now ready for departure, with everyone aboard heading to M78, the homeworld of the Ultras. The crew is cheered on as the spaceship lifts off, accompanied by jets carrying the elder heroes, as they embark on their next adventure beyond Earth’s atmosphere, symbolizing the never-ending spirit of hope and heroism that Ultraman embodies.
