The day that Takeshi Yamamoto died was, objectively speaking, a pretty terrible day.
It had started out normally enough. The twenty-three-year-old had woken up in his small Tokyo apartment, surrounded by the accumulated treasures of a man who had devoted his entire existence to the singular pursuit of Kamen Rider merchandise. Posters covered every available inch of wall space. Figures stood in meticulously organized rows on custom-built shelving units that he had constructed himself after watching approximately forty-seven tutorials on YouTube. His prized possession—a screen-accurate replica of the Build Driver complete with functioning LED lights and sound effects—sat in a glass display case that he cleaned every single day without fail.
Takeshi had always known, deep in the core of his being, in the very fiber of his soul, in the metaphysical essence that comprised his consciousness, that Kamen Rider Build was objectively the best Rider ever created.
This was not an opinion. This was a fact. A law of the universe as immutable as gravity or the speed of light or the absolute certainty that any pizza ordered past midnight would taste inexplicably better than one ordered at a reasonable hour.
Build had everything. The genius protagonist who was also kind and determined. The incredible suit designs that combined the aesthetic brilliance of red and blue in ways that should not have worked but absolutely did. The fascinating scientific theming that made Takeshi actually enjoy chemistry for the first time in his life. The best match forms. The Hazard forms. The Genius form that was literally covered in the periodic table of elements because Sento Kiryu was that much of a beautiful nerd.
And the power scaling. Oh, the power scaling.
Takeshi had spent countless hours on forums and message boards, arguing with people who simply did not understand. Build had fused with Zi-O, the king of time itself. Build had defeated Decade, the Destroyer of Worlds, the Rider who could literally become any other Rider. Build's Genius form operated on a level of scientific understanding that approached the metaphysical. The man had created an entirely new universe through the power of physics and sheer determination.
How could anyone argue that any other Rider was better?
They couldn't. That was the answer. They simply could not.
On this particular morning, Takeshi had gone about his usual routine. He had eaten breakfast while watching episode twenty-seven of Kamen Rider Build for what was definitely the forty-third time. He had taken a shower while mentally reciting the lyrics to "Be The One" in their entirety, including the parts where he had to make up words because he had never actually looked up the official lyrics. He had gotten dressed in his Nascita Café t-shirt that he had imported from Japan at a price that was, frankly, unreasonable.
And then he had left his apartment to go to his job at the convenience store down the street, which was boring and unfulfilling but paid the bills that allowed him to continue purchasing Kamen Rider merchandise.
The truck had come out of nowhere.
Well, that wasn't entirely accurate. The truck had come out of a side street where trucks were definitely not supposed to be driving at that speed. It had run a red light. It had been driven by a man who had fallen asleep at the wheel after working three consecutive shifts because capitalism was a fundamentally broken system that prioritized productivity over human safety.
Takeshi had heard the horn blaring. He had turned. He had seen the massive vehicle bearing down on him with the inevitability of a freight train and the stopping power of absolutely nothing.
His last thought, before the impact, was that this was a really stupid way to die.
His second-to-last thought was that at least he was wearing his Build shirt.
And then there was darkness.
Consciousness returned to Takeshi in stages.
First, there was awareness—a vague sense of existing, of being something rather than nothing. It was like waking up from a very deep sleep, the kind where dreams blurred into reality and reality blurred into whatever strange dimension existed between the two.
Second, there was sensation. He could feel things. His body—and it was definitely a body, with arms and legs and a torso and all the other components that typically comprised a human form—was lying on something hard and cold. Concrete, maybe. Or asphalt. Something urban and unforgiving.
Third, there was confusion. Because the last thing he remembered was being hit by a truck at what he estimated to be approximately fifty kilometers per hour, and generally speaking, people who were hit by trucks at fifty kilometers per hour did not wake up lying on concrete feeling perfectly fine.
Fourth—and this was where things started to get really weird—there was the awareness that his body did not feel like his body.
Takeshi opened his eyes.
The sky above him was dark, tinged with the orange glow of artificial light pollution. Stars were visible but faded, struggling to compete with the urban illumination that emanated from somewhere beyond his immediate field of vision. A crescent moon hung low on the horizon, partially obscured by the silhouettes of buildings that stretched impossibly high into the night.
Those buildings did not look like Tokyo.
Takeshi sat up, and as he did, he became acutely aware of several facts that did not make any sense.
First: his hands were different. They were still hands, obviously, but they were not his hands. They were slightly larger, with longer fingers and a different pattern of lines across the palms. They were also, he noted with some confusion, wrapped in fingerless gloves that he definitely did not remember putting on.
Second: his clothes were different. He was wearing a white lab coat over a simple black shirt and gray pants. On his feet were shoes that looked comfortable and practical, the kind of footwear worn by someone who expected to do a lot of walking or, potentially, running.
Third: he was not in Tokyo. He was in an alley, flanked on both sides by brick walls covered in faded graffiti. At the end of the alley, he could see a street illuminated by neon signs and flickering streetlights. The signs were in English. Not Japanese. English.
Fourth—and this was the fact that made Takeshi's brain completely short-circuit—there was something attached to his waist.
He looked down.
His heart stopped.
Attached to his belt—no, serving as his belt—was the Build Driver.
Not a replica. Not a toy. Not a costume piece purchased from a convention vendor for an amount of money that he probably should have spent on rent instead.
The actual Build Driver.
Takeshi stared at it for a long, long moment. His brain attempted to process what he was seeing and failed spectacularly. Then it tried again. And failed again. On the third attempt, his brain simply gave up and decided to accept the situation at face value because the alternative—descending into a full existential crisis while sitting in an alley in what was apparently a foreign country—seemed counterproductive.
"What," Takeshi said aloud, and his voice was not his voice.
It was similar to his voice. It had the same general timbre and tone. But it was different in ways that he could not immediately articulate. Slightly deeper, maybe. More confident, somehow, in a way that voices should not be able to convey but absolutely did.
"What the actual hell."
He reached down with trembling fingers and touched the Build Driver. It was solid. Real. The metal and plastic components were exactly as he had always imagined they would feel, based on the hundreds of hours he had spent watching transformation sequences and imagining what it would be like to actually perform one.
And attached to the side of the Driver, held in place by a carrier mechanism that had definitely not been there a moment ago, were two FullBottles.
Rabbit.
And Tank.
RabbitTank.
The Best Match.
The original. The iconic. The combination that had defined an entire era of Kamen Rider history and established the foundational aesthetic that all subsequent Build forms would be compared against and found wanting because nothing could ever be as perfectly balanced as the rabbit's speed and the tank's power.
Takeshi picked up the Rabbit FullBottle and held it in front of his face. It was beautiful. The red plastic casing gleamed under the ambient light. The rabbit icon engraved on the surface seemed to glow with an internal luminescence that defied logical explanation. He could feel something inside the bottle, some kind of essence or energy that hummed against his palm like a living thing.
He turned the bottle slowly, examining it from every angle. Then he did the same with the Tank FullBottle, marveling at the blue coloring and the military iconography that conveyed power and durability and the fundamental concept of being able to roll over your enemies with the unstoppable force of armored warfare.
"I died," Takeshi said slowly, speaking the words aloud because doing so made them seem more real. "I got hit by a truck. And now I'm... I'm somewhere else. In a different body. With the Build Driver."
He paused, considering the implications.
"Am I dreaming? Is this a coma? Did I actually survive and this is some kind of weird brain-damage-induced hallucination?"
He pinched himself. It hurt.
"Okay, not a dream. Probably not a hallucination. Although I guess if it was a hallucination, the hallucination would include realistic pain responses because my brain would expect pinching to hurt."
He stood up, wobbling slightly as he adjusted to legs that were familiar but not quite right. His center of gravity was different. His height was different—he was taller now, by at least a few centimeters. His entire physical form was different in ways both subtle and profound.
But the Build Driver was still attached to his waist. The FullBottles were still in his hands. And that meant that whatever else was happening, one thing was definitely true:
He was Kamen Rider Build now.
The realization hit him like a second truck, except this truck was made of pure euphoria instead of metal and momentum.
"I'm Build," Takeshi whispered, his voice filled with religious awe. "I'm actually Kamen Rider Build. I have the Driver. I have the bottles. I can transform."
He looked around the alley, suddenly very aware that he was standing in an unknown location in an unknown city in what appeared to be an unknown world. The English signage suggested he was somewhere in an English-speaking country. The architectural style—visible through the gap at the end of the alley—suggested America, maybe. Or possibly England. Or Australia. Or any number of other places where people spoke English and built brick buildings.
But first things first.
He needed to test the Driver.
Takeshi had practiced this moment approximately ten thousand times. In his bedroom. In front of the mirror. In the shower. During boring meetings at work when his boss was droning on about inventory management and his mind was wandering to far more important topics.
He knew the sequence by heart.
He took a deep breath.
He shook the Rabbit FullBottle, activating the component inside. The red liquid sloshed visibly through the transparent portions of the casing, and he could feel the energy within responding to the motion, charging up like a battery preparing to discharge.
He did the same with the Tank FullBottle, watching as the blue liquid inside swirled and churned with kinetic anticipation.
Then, with the reverence of a priest performing a sacred ritual, he inserted the bottles into the Build Driver.
RABBIT! TANK!
The electronic voice that emerged from the Driver was exactly as it had always sounded in the show. Deep and authoritative, with a slight mechanical undertone that conveyed technological sophistication. The sound resonated through the alley, echoing off the brick walls and filling the space with auditory confirmation that this was really happening.
Takeshi reached for the Vortex Lever on the side of the Driver. His fingers closed around the crank, and he could feel the mechanism waiting to be activated, thrumming with barely-contained potential energy.
"Are you ready?" he asked, because he was absolutely required to ask that question. It was tradition. It was ritual. It was the law.
He did not wait for an answer.
He cranked the lever.
HAGANE NO MOONSAULT! RABBITTANK!
The music that burst from the Driver was indescribable in its perfection. A guitar riff that transcended the boundaries of mere sound and ascended into the realm of pure artistic expression. Drums that pounded with the heartbeat of a universe preparing to witness something incredible.
The transformation began.
From the Driver, two halves of a suit materialized out of what could only be described as pure mathematical formula. Equations and scientific notations swirled through the air like visible representations of physics itself, coalescing into solid matter through processes that defied every law of thermodynamics that Takeshi had ever learned.
The left half of the suit was red—Rabbit Red, as bright and vibrant as fresh blood or a sunset or the color of passion itself. It was sleek and aerodynamic, designed for speed and agility, with a spring-loaded mechanism visible in the leg that promised the ability to leap incredible distances.
The right half of the suit was blue—Tank Blue, as deep and solid as the ocean or the sky at twilight or the color of unshakeable determination. It was angular and armored, designed for power and defense, with treaded components visible that evoked the relentless forward momentum of military machinery.
The two halves came together around Takeshi's body, merging seamlessly at the center line to form a complete suit that was neither fully rabbit nor fully tank but something greater than the sum of its parts. A Best Match. A perfect combination.
The helmet materialized last, encasing his head in protective armor with compound eyes that divided into red and blue sections. Antennae extended from the red side while a tank barrel protruded slightly from the blue, both elements integrating into the overall design with flawless aesthetic coherence.
Takeshi—no, not Takeshi anymore. He was someone new now. Someone who had been reborn in fire and formula, transformed from ordinary human to extraordinary hero.
He was Kamen Rider Build.
"YEEEEEESSSSSS!"
The scream that erupted from his helmet's voice modulator was entirely undignified and completely appropriate given the circumstances. He threw his arms into the air, fists clenched in triumph, and began jumping up and down with the unbridled enthusiasm of a child receiving exactly what they wanted for Christmas.
"IT WORKED! IT ACTUALLY WORKED! I'M BUILD! I'M KAMEN RIDER BUILD!"
He stopped jumping and held his hands in front of his face, examining the armored gauntlets that now covered his fingers. He flexed experimentally, marveling at how natural the movement felt. The suit moved with him, responding to his intentions as smoothly as his own skin. It was as though the armor had been designed specifically for him, tailored to his exact dimensions and fighting style despite the fact that he had no actual fighting style to speak of.
"The Laws of Victory," he declared, because he needed to say it. He physically required the words to leave his mouth. "Have been decided!"
His voice echoed through the alley, and somewhere in the distance, a car alarm began to wail.
Takeshi looked toward the end of the alley, where the street and its mysterious English signage awaited. He had so many questions. Where was he? How had he gotten here? Why did he have the Build Driver? Was this a parallel universe? A different dimension? Some kind of elaborate afterlife designed specifically to reward Kamen Rider fans who had been killed by negligent truck drivers?
But those questions could wait.
Right now, in this moment, he was wearing the most beautiful suit of armor ever designed by human imagination. He had the power of science and mathematics literally manifested around his body. He was, for the first time in his entire existence, actually cool.
He was going to enjoy this.
The city, Takeshi discovered as he emerged from the alley, was Gotham.
He knew this because there was a massive sign on the building across the street that read "GOTHAM GAZETTE" in bold letters. There were also several smaller signs advertising various businesses and services, all of which included the word "Gotham" in their names. Gotham Pizza. Gotham Dry Cleaning. Gotham Bail Bonds, which seemed ominous.
Gotham.
As in Gotham City.
As in the city where Batman lived.
Takeshi stood on the sidewalk, still fully transformed, his compound eyes taking in the urban landscape with a mixture of awe and existential confusion that was becoming increasingly familiar.
He was in the DC Universe.
The actual DC Universe.
The universe where Superman could bench press planets and Wonder Woman had been blessed by literal gods and the Flash could run faster than the speed of light which didn't even make any kind of scientific sense but that was fine because comic book physics had never really been concerned with logical consistency.
And he was Kamen Rider Build.
"Okay," he said aloud, his voice modulated through the helmet's speakers. "Okay. This is fine. This is completely fine. I died and was reborn in a fictional universe as my favorite fictional character. That's a totally normal thing that happens to people. I'm sure there's a perfectly reasonable explanation for all of this."
There was not, in fact, a perfectly reasonable explanation for any of this. But Takeshi had decided that he was going to operate under the assumption that one existed, because the alternative was accepting that the universe was fundamentally absurd and that nothing made sense, which was a philosophical position that he did not have time to fully explore at this particular moment.
A woman walked past him on the sidewalk. She glanced at him, did a double-take, and then hurried away with the speed of someone who had lived in Gotham long enough to know that weird costumes usually meant trouble.
"Fair enough," Takeshi muttered.
He looked down at himself, still marveling at the RabbitTank suit. The armor gleamed under the streetlights, the red and blue sections catching and reflecting illumination in ways that made him look like a walking Christmas decoration—if Christmas decorations were incredibly badass and capable of punching through concrete.
He needed to figure out what to do next. He was in a strange city in a strange world, wearing a suit of armor that gave him superhuman capabilities, and he had no identification, no money, no place to stay, and no idea how any of this had happened.
But he was also Kamen Rider Build, which meant he had access to the genius-level intellect that came with being the wielder of the Fullbottles. Sento Kiryu had been a brilliant physicist, capable of creating technology that bordered on the miraculous. Surely some of that intelligence had transferred along with the Driver and the suit.
Takeshi closed his eyes inside the helmet and tried to think like a genius.
...
Nothing happened.
He tried again, concentrating harder.
...
Still nothing.
"Right," he said. "So I'm Build, but I'm not actually Sento. I'm still me. Just... me with the Build Driver. That's... that's probably fine. I watched every episode of the show at least three times. I know how everything works. I don't need to be a genius physicist. I just need to remember what a genius physicist would do."
This logic was, objectively speaking, terrible. But it was all he had.
A scream cut through the night air.
Takeshi's head snapped toward the source of the sound automatically, his body reacting before his mind had fully processed what he was hearing. The scream had come from somewhere to his left, down a side street that led into a darker, less well-lit section of the city.
For a moment—just a brief moment—he hesitated. He was not a hero. He had never been a hero. He was a convenience store clerk who watched too much Kamen Rider and spent too much money on merchandise. He had never been in a fight in his life. He had no combat training. He had no idea if he could actually use the abilities that the Build suit theoretically provided.
But he was wearing the suit. He had the power. And someone was in trouble.
In Kamen Rider Build, Sento had always rushed toward danger without hesitation. He had always put himself at risk to protect others. He had been a hero not because he was powerful, but because he was willing to act when action was needed.
Takeshi might not be Sento Kiryu.
But he could try to be.
He ran.
The source of the scream was a mugging in progress, because of course it was. This was Gotham City. Muggings were probably the city's primary form of entertainment, given how frequently they seemed to occur in every Batman comic and movie and television show ever created.
Three men had cornered a young woman against the wall of a closed storefront. They were dressed in the universal uniform of low-level criminals everywhere: dark hoodies, baggy pants, and expressions of malicious intent that made their intentions abundantly clear.
"Just give us the purse, lady," one of them was saying as Takeshi rounded the corner. "We don't want to hurt you."
This was clearly a lie. They very obviously wanted to hurt her, or at least didn't particularly care if they did. The knife in the speaker's hand made this point rather emphatically.
"HEY!"
The shout emerged from Takeshi's helmet before he had consciously decided to make it. The three muggers turned, their expressions shifting from predatory confidence to confusion as they took in the sight before them.
A figure stood at the entrance to the alley. It was humanoid, but clearly not human—the armor covering its body was too seamless, too alien in its design. One half was red, the other blue, divided perfectly down the middle. Compound eyes gleamed with inner light. Antennae and mechanical components jutted from the helmet in a configuration that defied immediate categorization.
"What the hell?" one of the muggers said.
"Is that a new Batman thing?" another asked.
"I don't know, but it's ugly as sin."
That last comment cut deep. The RabbitTank suit was not ugly. It was a masterpiece of aesthetic design. It was the perfect fusion of organic and mechanical elements. It was art.
"Ugly?!" Takeshi's voice came out louder and more offended than he had intended. "This suit is beautiful! It's a scientific miracle! It represents the pinnacle of Best Match theory!"
The muggers exchanged confused looks.
"Is he okay?" the first one asked.
"Who cares?" The one with the knife stepped forward, waving the blade in a way that was probably supposed to be threatening. "Look, weirdo, I don't know what your deal is, but you should turn around and walk away. We're just conducting some business here."
Takeshi looked at the knife. Then he looked at his armored hands. Then he looked back at the knife.
The math was not complicated.
"Here's what's going to happen," he said, surprised by how confident his voice sounded despite the fact that his heart was pounding against his ribs like a prisoner trying to escape. "You're going to drop the knife. You're going to let her go. And then you're going to leave. Because if you don't..."
He paused for dramatic effect.
"...I'm going to have to begin the experiment."
The words felt right coming out of his mouth. They felt like something Sento would say. Something Build would say.
The mugger with the knife laughed. "Yeah? And what experiment would that be?"
Takeshi smiled inside his helmet.
"The experiment," he said, "to determine how many Best Matches it takes to defeat three idiots."
He moved.
The thing about the RabbitTank Best Match was that it combined speed and power in perfect equilibrium. The Rabbit side provided incredible agility and reflexes, the ability to move faster than the eye could track. The Tank side provided strength and durability, the ability to take hits and deliver them back with devastating force.
Takeshi had never been in a fight before.
But Build had been in hundreds.
And the suit, it seemed, knew what to do.
His body moved with a fluidity that he had never experienced in his previous life. He crossed the distance between himself and the knife-wielding mugger in less than a second, his Rabbit-enhanced legs propelling him forward with spring-loaded momentum that made him feel like he was flying.
His right fist—the Tank side—connected with the mugger's midsection before the man had even finished flinching. The impact was solid and satisfying, a meaty thud of armored knuckles meeting unarmored flesh. The mugger doubled over, the knife clattering to the ground, all the air rushing out of his lungs in a single explosive wheeze.
Takeshi didn't stop. He spun, using the momentum of his punch to carry him into a roundhouse kick that caught the second mugger in the shoulder. The Rabbit leg provided the speed and flexibility; the impact provided the rest. The second mugger went flying sideways, colliding with a dumpster with a crash that echoed through the alley.
The third mugger, displaying the survival instincts that had kept humanity alive through millennia of predation and violence, turned and ran.
He made it approximately three steps.
Takeshi jumped.
The Rabbit leg's spring mechanism activated, launching him into the air with a force that would have been impossible for any unarmored human. He arced over the fleeing mugger's head, tucking into a flip that he absolutely should not have known how to perform, and landed in front of the man with the graceful precision of a trained acrobat.
"Going somewhere?" he asked.
The mugger screamed and tried to change direction. He succeeded only in tripping over his own feet and crashing face-first into the asphalt.
Takeshi looked at the three incapacitated criminals. The first one was still curled up on the ground, clutching his stomach and making sounds that suggested breathing was currently a challenge. The second was slumped against the dumpster, unconscious or pretending to be. The third was lying face-down in a pose that indicated he had given up on the concept of resistance entirely.
"Huh," Takeshi said.
That had been... easy.
Really easy.
Easier than he had expected, certainly. He had assumed there would be more difficulty involved. More struggle. More dramatic tension. But these were just ordinary human criminals with no special abilities or advanced weaponry, and he was wearing a suit that had been designed to fight monsters and other Kamen Riders and the occasional interdimensional threat.
It was not exactly a fair fight.
He turned to the woman who had been the target of the mugging. She was pressed against the wall, her eyes wide, her expression a mixture of fear and confusion and something that might have been gratitude.
"Are you okay?" he asked.
She nodded, unable to speak.
"Good. That's good." He looked around awkwardly. "You should, um, probably call the police. Or something. They'll want to arrest these guys, I assume."
She nodded again.
"Okay. Great. I'm going to... go now. Because there might be other crimes happening. In other places. That I should also stop. Because I'm a hero now, apparently. That's a thing I do."
He was rambling. He knew he was rambling. But his adrenaline was pumping and his brain was struggling to process the fact that he had just won his first fight and he had absolutely no idea what proper superhero protocol was in situations like this.
"Who are you?" the woman finally managed to ask.
It was a good question.
He could say his real name. His human name, from his previous life. But that didn't seem right. He wasn't Takeshi anymore. He was something new. Something different.
He was Build.
"Kamen Rider Build," he said, the words feeling natural and right. "Remember that name. The laws of victory have been decided."
And then, because he had no idea how to make a cool exit and standing around waiting for the police seemed awkward, he jumped.
The Rabbit leg launched him upward with incredible force. He cleared the top of the three-story building beside him easily, landing on the roof with a grace that surprised even himself. Below, he could hear the woman calling out in amazement, asking where he had gone, what he was.
He did not answer.
He was too busy grinning inside his helmet.
"That was amazing," he said to himself, to the city, to the universe that had given him this impossible gift. "That was absolutely amazing."
He looked out over the rooftops of Gotham City, seeing the urban landscape stretched before him like a playground waiting to be explored. Somewhere out there, crimes were being committed. People were in danger. The forces of evil were doing evil things.
And he was going to stop them.
Because he was Kamen Rider Build.
The best Rider.
The coolest Rider.
The Rider who had fused with Zi-O and beaten Decade and created an entirely new universe through the power of physics and determination.
And this world had no idea what was about to hit it.
The next several hours were educational.
Takeshi—or Build, as he was beginning to think of himself—patrolled the streets and rooftops of Gotham City with the enthusiasm of a child in a candy store. A candy store where all the candy was criminals and the act of eating candy was actually punching people who deserved to be punched.
The analogy fell apart under scrutiny, but the point remained.
Gotham, he discovered, was even worse than the comics and movies had suggested. Crime was everywhere. Not just muggings and robberies, but drug deals and human trafficking and protection rackets and at least three separate incidents of arson. It was as if the entire city had decided that the concept of law and order was merely a polite suggestion rather than an actual societal expectation.
Build threw himself into the work with abandon.
He stopped a car theft in progress, using his Rabbit-enhanced speed to catch up with the fleeing vehicle and his Tank-enhanced strength to simply lift the front end off the ground until the thief surrendered out of sheer confusion. He interrupted a drug deal in an abandoned warehouse, discovering in the process that the Build suit's compound eyes had some kind of low-light vision capability that allowed him to see perfectly in the darkness. He prevented a shooting by literally jumping in front of the bullet, feeling it ping harmlessly off his armored chest like a mild annoyance rather than a lethal projectile.
That last one had been a bit of a gamble. He hadn't been entirely sure the suit would stop a bullet. But it had, and now he knew, and that knowledge was valuable.
Throughout it all, the city reacted to him with a mixture of fear and bewilderment. Gotham was no stranger to costumed vigilantes—Batman had been operating here for years, after all—but Build was clearly something different. His armor was too sophisticated. His movements were too precise. And his constant declarations about "Best Matches" and "experiments" and "the laws of victory" left witnesses confused and slightly concerned about his mental state.
He didn't care.
He was having the time of his life.
It was during his fourth hour of patrol, as he was perched on the edge of a skyscraper and contemplating whether to investigate a suspicious-looking van that had been circling the same block for twenty minutes, that he heard the explosion.
The sound was massive, a thunderous boom that echoed across the city and rattled windows for blocks in every direction. Build spun toward the source, his compound eyes zooming in automatically to reveal a column of smoke rising from a building approximately two miles to the east.
Fire was visible at the base of the smoke column, orange and red licking at the structure with hungry intensity. Even from this distance, he could see that the building was large—some kind of industrial complex, maybe, or a research facility. The kind of place that would have a lot of equipment and chemicals and other things that could cause secondary explosions if the fire spread.
Build didn't hesitate.
He jumped from the skyscraper, his Rabbit leg launching him across the urban landscape in a series of bounds that covered the two miles in less than a minute. Each jump carried him hundreds of meters, the spring-loaded mechanism in his leg compressing and releasing with mechanical precision. The wind rushed past his helmet, the city blurring beneath him, and he felt alive in a way that his previous existence had never allowed.
He landed in the street outside the burning building, the asphalt cracking beneath the force of his impact. Immediately, he could see that the situation was worse than he had initially thought.
The building was a research facility of some kind—STAR Labs, according to the singed sign hanging crookedly above the main entrance. And it wasn't just on fire. Parts of it were actively exploding, secondary detonations going off at irregular intervals as the flames reached whatever volatile materials were stored inside.
But that wasn't the worst part.
The worst part was the figure standing in the middle of the destruction, laughing.
He was tall, easily seven feet, with a muscular build that suggested either extensive time in the gym or extensive exposure to whatever chemical or scientific process had turned him into what he currently was. His skin was orange, textured like bark or perhaps stone, and flames danced along his surface like a living aura. His eyes glowed with the same orange fire, and his mouth—twisted into a grin of pure malicious joy—revealed teeth that seemed to be made of burning coals.
Build had never seen this villain before. He wasn't one of the famous ones—not Joker or Two-Face or Bane or any of the rogues gallery that he remembered from the comics. But the man was clearly dangerous, clearly powerful, and clearly responsible for the destruction unfolding around him.
"YES!" the burning man screamed, throwing his arms wide. "BURN! BURN IT ALL! LET THE FLAMES CONSUME EVERYTHING!"
Okay. So he was dealing with a crazy person. A crazy person who was also on fire and apparently immune to the effects of said fire.
This was going to be harder than the muggers.
Build stepped forward, his armored feet crunching on debris that had been scattered across the street by the explosions. The movement caught the burning man's attention, and those glowing eyes turned toward him with a mixture of curiosity and contempt.
"Who the hell are you?" the villain demanded.
Build struck a pose. It was automatic, instinctive. The pose Sento always struck when confronting an enemy for the first time. Left hand extended, palm up. Right hand raised, fingers pointing toward the sky. Feet planted, shoulders back.
"Kamen Rider Build," he announced. "The handsome genius physicist who's about to kick your ass."
He wasn't actually a physicist. He had failed physics in high school. But the line sounded cool and that was what mattered.
The burning man stared at him for a long moment. Then he burst into laughter.
"Kamen Rider? What kind of stupid name is that? Are you supposed to be some kind of motorcycle-themed hero?"
Build's eye twitched behind his helmet.
"It's not—that's not—the name doesn't—" He took a deep breath, forcing himself to calm down. "You know what? I don't have time to explain the cultural significance and decades-long history of the Kamen Rider franchise to someone who's clearly too stupid to appreciate it. Let's just skip to the part where I beat you up."
The burning man's laughter cut off abruptly. His expression shifted from amused to angry with a speed that suggested he had very limited emotional regulation.
"Beat me up?" he snarled. "You think you can beat me up? I am Inferno! I have the power of fire itself! I am unstoppable! I am invincible! I am—"
"Standing around monologuing while I get ready to punch you," Build interrupted. "Yeah, I noticed."
Inferno—God, what a generic name—roared with rage and thrust both hands forward. Twin jets of flame erupted from his palms, screaming toward Build with enough force and heat to melt steel.
Build moved.
The RabbitTank suit responded to his intentions with flawless precision, his Rabbit-enhanced reflexes kicking in at the exact moment they were needed. He dove to the side, the flames passing close enough that he could feel the heat even through his armor, and rolled back to his feet in a single fluid motion.
"Okay," he said, "so you're the ranged attack type. Good to know."
He ran toward Inferno, zigzagging to avoid the streams of fire that the villain was now launching at him with increasing desperation. The flames were intense—hotter than anything Build had experienced in his previous life—but the suit seemed to be holding up. The armor wasn't designed for extreme heat, but it was resilient enough to withstand brief exposure.
He closed the distance in seconds, his Rabbit leg propelling him forward with spring-loaded bursts of speed. Inferno tried to create a wall of fire between them, but Build simply jumped over it, somersaulting through the air and coming down with a flying kick aimed directly at the villain's chest.
The impact was significant.
Build felt the force of the collision travel up his leg and into his body, absorbed and distributed by the suit's internal mechanisms. Inferno staggered backward, his feet leaving furrows in the asphalt as he tried to maintain his balance.
"What—" the villain gasped, clearly not expecting his opponent to actually reach him. "How did you—"
Build didn't give him time to finish the question. He launched a combination attack, his fists moving in patterns that he was pulling from half-remembered fight scenes from the show. Left jab. Right cross. Left hook. Right uppercut. Each blow connected with satisfying solidity, the Tank-enhanced power behind them making Inferno stumble and retreat.
But the villain was tough. Tougher than Build had expected. The punches were landing, but they weren't doing enough damage. Inferno's strange orange skin seemed to absorb and redistribute the force somehow, preventing any single blow from being decisive.
And the fire was getting hotter.
Inferno roared, and his entire body erupted into a blazing inferno—hence the name, apparently—that forced Build to leap backward or risk being incinerated. The heat was intense, washing over him in waves that made even the armored suit feel uncomfortably warm.
"ENOUGH!" Inferno screamed. "I don't know what kind of fancy armor you're wearing, but nothing can withstand my flames! Nothing!"
He thrust both hands forward, and this time the fire that emerged wasn't just a jet or a stream. It was a tsunami, a wall of flame that expanded outward in all directions with the force of an explosion.
Build had approximately half a second to react.
He couldn't dodge—the wall was too wide, too fast, coming from too many directions at once. He couldn't tank it—the heat was already almost too much, and this was clearly meant to be a finishing attack.
But he could do something else.
His hands moved to the Build Driver, fingers finding the FullBottles with practiced ease. In one smooth motion, he ejected the Rabbit and Tank bottles and replaced them with two different ones.
Where had these bottles come from? He didn't know. They had simply been there when he needed them, attached to the carrier at his waist, waiting to be used.
He inserted them into the Driver.
DIAMOND! GATLING!
TENKUU NO ABARENBOU! DIAMONDGATLING!
The transformation happened in an instant. The RabbitTank armor dissolved into mathematical formulae and scientific notation, and new armor took its place. The left side was now clear and crystalline, faceted like a cut gemstone, refracting light in a thousand directions. The right side was gray and mechanical, dominated by a rotating gatling gun barrel mounted on the forearm.
The wall of fire hit him.
And did nothing.
The Diamond half of the suit was designed for defense, its crystalline structure incredibly resistant to heat, pressure, and impact. The flames washed over him like water over a stone, unable to penetrate, unable to harm, unable to do anything except waste Inferno's energy.
Build stood in the center of the firestorm, completely unharmed.
"What?!" Inferno's voice was audible even over the roar of the flames. "That's impossible! Nothing can withstand—"
"Wrong," Build interrupted. "Some things can withstand. The laws of science allow for many possibilities that your limited understanding can't comprehend."
He raised his right arm, the Gatling barrel spinning up with a mechanical whine that was audible even over the flames.
"Let me demonstrate."
The Gatling fired.
Bullets—energy bullets, bright blue and crackling with power—erupted from the barrel at a rate of approximately three thousand rounds per minute. They tore through the dying flames of Inferno's attack and slammed into the villain's body with the relentless precision of a metronome.
Inferno screamed, trying to raise his arms to defend himself, but there was no defense against this kind of assault. The bullets weren't designed to penetrate—they were designed to impact, each one carrying a payload of kinetic force that stacked with every hit. One bullet was nothing. Ten bullets were a nuisance. A hundred bullets were a problem.
A thousand bullets were a defeat.
By the time Build stopped firing, Inferno was on his knees, his orange skin cracked and dimmed, his flames reduced to mere embers. He looked up at the armored figure standing before him with an expression of total disbelief.
"How?" he whispered. "How did you...?"
Build walked toward him, each step deliberate and confident. He had won. He knew he had won. And he was going to make sure Inferno knew it too.
"Science," he said. "The answer is always science. Your flames are impressive, but they're just thermal energy. And thermal energy can be countered, redirected, nullified. All it takes is the right materials, the right approach, the right..."
He paused for effect.
"...Best Match."
Inferno tried to rise, tried to gather his power for one last attack. But he was too weakened, too drained, too thoroughly defeated.
Build reached for the Build Driver one more time.
"Now," he said, "let's finish this experiment."
He cranked the Vortex Lever.
READY, GO! VOLTECH FINISH!
Energy surged through his body, concentrating in his right leg—the Gatling leg, because the finishing move drew power from the entire suit regardless of which specific components were active. He jumped into the air, the energy crackling around him like lightning, and descended toward Inferno in a flying kick that carried the cumulative force of everything the DiamondGatling form could generate.
The impact was spectacular.
Inferno went flying backward, crashing through the ruined wall of the STAR Labs building and disappearing into the smoke and debris within. The explosion that followed suggested he had hit something else explosive on the way, but Build was reasonably confident that the villain would survive. These superpowered types usually did.
He landed in a crouch, one hand touching the ground for stability, his armor gleaming in the light of the dying fires. Around him, the sounds of emergency sirens were approaching—fire trucks and ambulances and police, no doubt responding to reports of the explosion and the battle.
Build stood up and dusted off his armor, a gesture that was entirely unnecessary but felt appropriately cool.
"Well," he said to no one in particular, "that was fun."
The aftermath of the STAR Labs battle was complicated.
Police and firefighters arrived in force, swarming over the scene with the organized chaos of professionals responding to an emergency. Build watched from a nearby rooftop as they worked, not entirely sure whether he should stick around or disappear before anyone started asking questions.
In the end, the decision was made for him.
"Nice work."
The voice came from behind him, and Build spun around with his guard up, ready for another fight.
But the figure standing on the rooftop wasn't a villain.
He was wearing a cape. A long, black cape that seemed to absorb the light around it, making him appear more shadow than substance. His suit was similarly dark, form-fitting armor that covered his body from neck to toe. A cowl obscured the upper half of his face, leaving only a strong jaw and a thin-lipped mouth visible. The pointed ears that rose from the cowl were unmistakable.
Batman.
Actual, literal Batman.
The Dark Knight of Gotham City, standing approximately ten feet away, looking at Build with an expression that might have been curiosity or might have been a prelude to violence.
Build's brain short-circuited for the second time that day.
"Oh my God," he said before he could stop himself. "You're Batman."
Batman's expression didn't change. "You know who I am."
"Of course I know who you are! You're Batman! The Batman! The world's greatest detective! The guy who punches clowns and has too many dead sidekicks!"
Okay, that last part had probably been inappropriate. But Build was too overwhelmed to filter his words properly.
Batman's eyes—visible through the cowl's lenses—narrowed slightly. "Who are you?"
"Kamen Rider Build. I said that already. To the fire guy. Inferno, he called himself. Generic name, but the powers were pretty cool, I guess. Fire manipulation. Heat generation. Enhanced durability. Probably some kind of metahuman or science experiment gone wrong. You'd know better than me. This is your city."
He was rambling again. He needed to stop rambling.
Batman continued to study him, and Build got the distinct impression that he was being analyzed, catalogued, assessed for threat potential. It was not a comfortable feeling.
"I've never seen technology like yours," Batman said finally. "The transformation sequence. The energy signatures. The way you changed forms mid-combat. None of it matches any known tech base."
"Yeah, it wouldn't." Build tapped the Build Driver. "This isn't from around here. It's from... somewhere else. Another universe, I think. Or another dimension. I'm still working out the specifics myself."
"Another universe."
"I know how it sounds. But trust me, the explanation is even weirder than that."
Batman stared at him for a long moment. Then, without changing his expression at all, he said: "You're not lying."
"You can tell that?"
"Body language. Voice modulation analysis through your helmet's speakers. Micro-expressions visible through your suit's eye covers. Everything indicates you genuinely believe what you're saying."
"That's... incredibly creepy," Build said. "And also impressive. Mostly creepy, though."
Something that might have been amusement flickered across Batman's face. Or it might have been indigestion. It was hard to tell with Batman.
"The League will want to know about you," he said. "A new hero with unknown capabilities appearing in Gotham isn't something that can be ignored."
"The League? As in the Justice League? As in Superman and Wonder Woman and the Flash and—" Build caught himself before he could go into full fanboy mode. "Right. Yes. Of course. That makes sense. I'm happy to meet with them. Answer questions. Prove I'm not a threat."
"You'll understand if we take precautions."
"Absolutely. Totally understand. I'd do the same thing in your position. Actually, I probably wouldn't, because I'm not paranoid enough, but I get why you are. The Joker and everything."
Batman's jaw tightened almost imperceptibly at the mention of the Joker. Build made a mental note not to bring up the clown again.
"There's a location. An address." Batman produced a small card from somewhere—his belt, probably, though Build hadn't seen him reach for it—and held it out. "Be there tomorrow at noon. Don't be late."
Build took the card. It had an address printed on it, nothing else. No name, no logo, no indication of what would be found there.
"And if I don't show up?" he asked, purely out of curiosity.
"I'll find you." Batman's voice carried absolute certainty. "And I'll find out everything I need to know. The easy way or the hard way. Your choice."
"Right. Noon. Tomorrow. Got it."
Batman turned and walked toward the edge of the rooftop. Then he paused and looked back over his shoulder.
"Build," he said.
"Yeah?"
"Good work tonight. The STAR Labs facility would have been a total loss if you hadn't intervened. You saved lives."
Before Build could respond, Batman stepped off the edge of the rooftop and disappeared into the night, his cape spreading like wings as he glided toward some unseen destination.
Build stood alone on the rooftop, holding the card in his armored hand, staring at the spot where the Dark Knight had vanished.
"I just met Batman," he said aloud. "I just had a conversation with actual Batman. And he told me I did good work."
He looked down at himself, at the DiamondGatling armor that still covered his body, at the Build Driver that had given him powers beyond anything he had ever imagined.
"This is the greatest thing that has ever happened to anyone in the history of anything," he declared.
Then he jumped off the rooftop and began making his way across the city, looking for more crimes to stop, more people to save, more opportunities to prove that he belonged in this world.
He was Kamen Rider Build.
And his story was just beginning.
The sun was rising over Gotham City when Build finally decided to take a break.
He had been patrolling for nearly twelve hours straight, stopping an average of one crime every twenty minutes, and even the superhuman stamina provided by the FullBottles couldn't completely eliminate fatigue. His body was tired. His mind was tired. His everything was tired.
But he was also happier than he had ever been in his entire existence.
He found a rooftop with a good view of the sunrise and sat down, his legs dangling over the edge, his armored back resting against an air conditioning unit. From this vantage point, he could see the city spread out below him—dirty and dangerous and beautiful in its own corrupt way.
This was his home now. His world. His responsibility.
The thought should have been terrifying. Instead, it was exhilarating.
"I'm going to figure this out," he said to himself, to the rising sun, to the universe that had given him this chance. "I'm going to find out why I'm here, how this happened, what I'm supposed to do. But more than that..."
He looked down at the Build Driver, at the FullBottles attached to his waist, at the suit that had become an extension of his own body.
"...I'm going to be the hero this world needs. Not because I have to. Not because someone is making me. But because I can. Because I have the power. Because I choose to use it."
He reached up and touched his helmet, triggering the detransformation sequence. The armor dissolved into mathematical formulae and scientific notation, leaving behind a young man in a white lab coat sitting on a Gotham City rooftop as the sun rose over the horizon.
His new body. His new life. His new beginning.
"Kamen Rider Build," he said, testing the name one more time. "The genius physicist who fights for love and peace."
He wasn't a physicist. He wasn't a genius. And he wasn't even sure what fighting for love and peace actually meant in practical terms.
But he was going to figure it out.
Because that was what heroes did.
And now, for the first time in his existence, he was a hero.
To Be Continued...