The sensation of falling lasted an eternity.
Kazuki Kadoya remembered dying—a truck, screeching tires, a flash of headlights, then darkness. What he didn't expect was the voice that echoed through the void afterward.
"Your journey isn't over, Traveler. Worlds are colliding. Powers beyond comprehension threaten the multiverse. You are needed elsewhere."
Then came the pain. His body felt like it was being torn apart and reassembled simultaneously, his consciousness stretched across dimensions before snapping back like an overstretched rubber band.
Now, he was falling through a kaleidoscope of realities—glimpses of worlds where heroes in colorful costumes battled villains with godlike powers, where ordinary humans lived alongside beings who could level cities with a thought.
His last coherent memory was clutching the Neo-Decadriver, his most treasured possession—a perfect replica of the transformation device from Kamen Rider Decade, his favorite show. He'd spent a small fortune on it, a collector's item that never left his side.
Then, impact.
Kazuki awoke with a gasp, his body jerking upright. His lungs burned as if he'd been underwater too long. Disoriented, he blinked rapidly, trying to process his surroundings. He was in an alley, the ground beneath him damp and littered with debris. Tall buildings towered overhead, blocking much of the evening sky.
But the sky wasn't right. Even between the skyscrapers, he could see it had an unnatural reddish tint.
"What the hell?" he muttered, his voice hoarse. This wasn't Tokyo. The architecture, the atmosphere—everything felt foreign yet strangely familiar.
As his vision cleared, he noticed something even more alarming. His body felt different—stronger, more resilient. Looking down at his hands, he realized they weren't his hands, at least not as he remembered them. They were still his, but somehow younger, more defined.
And there, secured to his waist by a belt that hadn't been there before, was the Decadriver—except it was no longer a replica. The device hummed with energy, its surface gleaming with an unearthly light that no toy could produce.
"Impossible," he whispered, fingers tracing the contours of the device.
A newspaper caught in the wind tumbled across the alley, stopping at his feet. The headline made his blood run cold:
FLOATING CITY IS THIS THE END OF THE WORLD?
Below it, a date: April 15, 2015.
And a city: Sokovia.
Kazuki's mind reeled. Ultron? The Avengers? These were comic book characters, fictional heroes and villains from a universe that existed only in the pages of Marvel Comics and Movies.
Yet here he was, sitting in an alley in what appeared to be the floating city Sokovia, in a world where superheroes were real—and apparently in the middle of a catastrophic event.
"I've been reincarnated," he said aloud, the realization washing over him like a cold wave. "Not just reincarnated—transported to the Marvel 616 Universe. During the Age of Ultron."
The implications hit him hard. If his knowledge of Marvel Comics served him right, this was one of the darkest periods in the 616 timeline—a time when the sentient AI Ultron had nearly conquered the world, decimating hero teams and killing countless innocents.
As if responding to his revelation, the Decadriver pulsed, and suddenly, knowledge flooded his mind. The device was real, its powers genuine. He could transform into Kamen Rider Decade, the Destroyer of Worlds, the Traveler between realities. More importantly, he could access the powers of other Riders, becoming a conduit for their abilities.
In his original world, these were just characters from a TV show. Here, in this new reality, they represented actual power—power that now belonged to him.
Standing on shaky legs, Kazuki took a few tentative steps toward the mouth of the alley. The sounds of the city were wrong—too quiet for New York. The distant rumble of explosions occasionally broke the eerie silence. The sky continued to glow that unnatural reddish hue.
A world of gods and monsters, heroes and villains. A world where power meant something very different than it did in his previous life. And right now, a world in crisis.
"Why am I here?" he wondered aloud. "What am I supposed to do?"
The Decadriver pulsed again, as if urging him forward. Kazuki took a deep breath and stepped out onto the sidewalk. The street was nearly deserted, with abandoned vehicles and signs of hasty evacuation everywhere.
In the distance, he could see the distinctive outline of the Baxter Building, home of the Fantastic Four, its upper floors damaged and smoking. Further downtown, the Xavier Institute's Manhattan branch showed signs of battle, its facade cratered and windows shattered.
This was Earth-616, the primary continuity of the Marvel Universe, in one of its darkest hours. he teleported with a aroura Curtain to sokovia
As he stood taking in the devastation, the ground shook. Kazuki stumbled, catching himself against a wall as a massive figure rounded the corner three blocks away. Even at this distance, he could recognize the unmistakable purple and green armor of a Sentinel—but not a traditional model. This one had been twisted, modified, its design now incorporating elements of Ultron's distinctive appearance.
"Adaptive Sentinel Program Mark VII engaged," the mechanized voice boomed across the empty streets. "Scanning for mutant and superhuman signatures."
Kazuki ducked back into the alley, heart pounding. The Sentinel's arrival confirmed his worst fears—this was indeed the Age of Ultron, when the AI had not only deployed his own forces but had also reprogrammed the mutant-hunting Sentinels to target all super-powered individuals.
As thoughts swirled, Kazuki felt the Decadriver pulse again. This time, when he looked down, he noticed something he'd missed before—a rider booker in his suit to the belt. Opening it revealed a stack of cards, each bearing the image of a different Kamen Rider.
"If I'm here during the Age of Ultron," he murmured, "then maybe I'm meant to change something. To help the heroes turn the tide."
The smart move would be to lay low, to observe and learn before revealing himself. But something told him that wasn't an option. Not here. Not now. Not when the world was literally falling apart around him.
Better to act than to hide.
A sudden explosion rocked the ground, much closer this time. Kazuki peered around the corner to see a small group of civilians running from a pair of Ultron drones. Behind them, desperately providing cover, was a young woman whose hands glowed with crackling energy—unmistakably one of the newer X-Men, probably a student caught in the chaos.
"Help them!" shouted a voice from above. Kazuki looked up to see a figure in blue swinging down on what appeared to be a line of solidified light. Reed Richards—Mr. Fantastic—stretched his body to incredible lengths as he landed beside Kazuki.
"You're just standing there! Are you with us or against us?" Richards demanded, his normally calm scientific demeanor replaced by the desperation of a man who had seen too much tragedy in too short a time.
Kazuki says with a smirk, "Me? I am Just a Kamen Rider passing by" showing his decade card
Before Richards could respond, Kazuki grasped the Decadriver with practiced movements that somehow felt as natural as breathing.
"Henshin," he declared.
The world exploded in magenta light as nine translucent silhouettes of different armored forms appeared around him before converging on his body. When the light faded, Kazuki stood transformed—clad in magenta and black armor with green compound eyes and a barcode-like pattern across his helmet.
Reed Richards' eyes widened in scientific curiosity despite the dire situation. "Fascinating. Some kind of extra-dimensional armor manifestation? The energy readings are unlike anything I've—"
Without waiting for a response, Decade charged forward, drawing a card from his riderbooker and sliding it into the driver.
"KAMEN RIDE: KUUGA!"
Another flash of light, and Decade's form shifted, the magenta armor replaced by red and black with golden horns—the form of Kamen Rider Kuuga, with all his incredible strength and fighting prowess.
As the Ultron drones turned their attention from the fleeing civilians to this new threat, Kazuki felt a strange calm settle over him. In his previous life, he'd been ordinary. Here, he had the potential to be extraordinary.
Kamen Rider Decade had arrived in the Marvel Universe during its darkest hour. And nothing would ever be the same again.
In the distance, a distinctive SNIKT sound cut through the air as a short, muscular figure with adamantium claws emerged from the shadows, eyeing the transformed newcomer with suspicious interest.
"Hey, Stretcho," Wolverine growled to Reed Richards, "who's the new guy?"
Behind him, a shimmer in the air revealed Susan Storm—the Invisible Woman—maintaining a force field around a group of younger mutants.
"I don't know, Logan," Reed replied, his scientific mind already calculating the possibilities this new variable introduced to their desperate situation. "But right now, I think he's exactly what we need."