The address on Batman's card led to a nondescript building in the heart of Metropolis.
Build—or rather, the young man who had been Takeshi Yamamoto and was now something else entirely—stood on the sidewalk outside, staring at the completely unremarkable structure with a mixture of confusion and suspicion. It looked like an office building. A boring, corporate, soul-crushing office building where dreams went to die and middle managers held meetings about meetings.
This could not possibly be the right place.
He checked the card again. 1938 Sullivan Street, Metropolis. This was definitely 1938 Sullivan Street. The numbers were right there on the door, brass digits slightly tarnished from weather and time.
"Maybe it's a secret entrance," he muttered to himself. "Like, I have to knock a specific pattern, or say a password, or—"
The door opened.
A woman stepped out, and Build's brain immediately began the process of short-circuiting that was becoming distressingly familiar. She was tall—almost as tall as he was in this new body—with dark hair pulled back from a face that belonged on ancient Greek sculptures. Her eyes were blue and piercing, carrying the weight of centuries behind them. She wore a red and gold outfit that left little to the imagination regarding her physical capabilities, and the tiara on her forehead gleamed in the morning sunlight.
Wonder Woman.
Actual, literal, honest-to-Zeus Wonder Woman.
Princess Diana of Themyscira.
The Amazonian warrior who had been fighting for truth and justice since before his grandfather was born.
"You must be Build," she said, and her voice was exactly as commanding and melodious as he had always imagined it would be. "Batman said you would be arriving at noon. You're early."
Build checked his phone—a device that had somehow appeared in his pocket overnight, already connected to this world's cellular network through means he did not understand and had decided not to question. It was 11:47 AM.
"I didn't want to be late," he said. "Batman seemed like the kind of guy who would hold lateness against me for the rest of my life. However long that might be, given that he's also the kind of guy who could probably end my life whenever he wanted."
Wonder Woman's lips curved into something that might have been a smile. "Bruce can be... intense. But his paranoia has saved countless lives over the years. We've learned to trust his judgment, even when his methods seem excessive."
"His methods seem very excessive. He analyzed my body language through my armor while I was transformed. I don't even know how that's possible. The suit should have masked everything."
"Bruce has his ways." She stepped aside, gesturing toward the door. "Please, come in. The others are waiting."
Build walked through the door and found himself in a lobby that was completely at odds with the building's exterior. Where the outside had been bland and corporate, the inside was sleek and technological, all clean lines and hidden lighting and materials that looked like they cost more than his previous life's annual salary.
A reception desk sat empty. Elevators lined the far wall. And standing near those elevators, clearly waiting for him, was a group of individuals who represented the most powerful beings on the planet.
Superman was there, of course—the big blue Boy Scout himself, tall and broad-shouldered and radiating an aura of wholesome goodness that made Build feel vaguely guilty about every questionable thing he had ever done in his life. His cape was exactly as red as it appeared in the comics, his 'S' shield exactly as iconic, his jawline exactly as chiseled.
The Flash was there too, vibrating slightly in place in a way that suggested he found the concept of standing still physically painful. His red suit was a blur of scarlet and gold, and his expression carried the easy humor of someone who had seen too much to take anything too seriously.
Green Lantern—Hal Jordan, if the brown hair and cocky stance were any indication—stood with his arms crossed, a green glow emanating faintly from the ring on his finger. He was examining Build with the assessing gaze of a test pilot evaluating an unfamiliar aircraft.
Aquaman loomed near the back of the group, his golden armor and trident making him look like he had stepped directly out of ancient mythology. Which, Build supposed, he sort of had. His expression was harder to read than the others—the perpetual scowl of a man who spent too much time dealing with surface-world nonsense.
And Batman was there, because of course Batman was there. He was lurking in the shadows near the wall, somehow finding darkness in a room that was aggressively well-lit, his cape wrapped around him like a portable hiding spot.
Martian Manhunter phased through the ceiling and landed silently beside Superman, his green skin and red eyes adding an appropriately alien element to the gathering. Cyborg was also present, half-human and half-machine, his robotic eye scanning Build with what was probably every sensor known to science.
And there, standing slightly apart from the rest with an expression of barely-concealed disdain, was a small figure in a Robin costume.
Damian Wayne.
The current Robin. Son of Batman. Grandson of Ra's al Ghul. The single most annoying character in the entire DC Universe, in Build's personal and absolutely correct opinion.
Build had read the comics. He knew everything there was to know about Damian Wayne. The arrogance. The superiority complex. The constant dismissal of everyone around him as inferior. The way he treated his fellow Titans and sidekicks as obstacles rather than allies. The insufferable attitude that came from being raised by assassins and never being taught proper social skills.
Build hated Damian Wayne.
This was not a strong word. It was the accurate word. In his previous life, Takeshi had engaged in many online arguments about the worst characters in comics, and Damian Wayne had always topped his personal list. The brat needed to be humbled. Needed to learn that being the son of Batman did not make him special. Needed to understand that there were people in the world who would not tolerate his nonsense.
People like Build.
But that confrontation could wait. Right now, he was standing in front of the Justice League, and he needed to make a good impression.
"Hi," he said, because he was apparently incapable of thinking of a more impressive opening. "I'm Build. Kamen Rider Build. You're all... very tall. Except for you." He pointed at Damian. "You're short. And young. Why is there a child here?"
Damian's expression shifted from disdain to outright hostility. "I am Robin. I have more combat experience than most adults. I have been trained since birth by the League of Assassins. I am—"
"Short," Build interrupted. "You're short. I wasn't asking about your resume. I was just observing a physical fact. You are short. This is not controversial."
The Flash made a sound that might have been a suppressed laugh. Batman's expression didn't change, but Build got the distinct impression that the Dark Knight was filing this interaction away for future reference.
"Perhaps," Wonder Woman said diplomatically, "we should move to the meeting room. There is much to discuss."
The meeting room was on the top floor of the building, accessible via an elevator that moved much faster than any elevator had a right to move. Build suspected that the entire building was some kind of disguised facility—a front for Justice League operations in Metropolis, maybe, or a secondary base for situations where the Watchtower was inconvenient.
The room itself was dominated by a large circular table with enough chairs for the entire League and then some. Screens covered the walls, displaying news feeds and data readouts and what appeared to be a real-time satellite view of the planet.
Build took a seat where indicated, noting that Damian had positioned himself directly across the table with an expression that suggested he was planning exactly how to murder Build and make it look like an accident.
Good. Let the little gremlin plan. Build had the power of science on his side.
"Let's start with the basics," Superman said, his voice carrying the natural authority of someone used to being listened to. "Batman's report mentioned that you claim to be from another universe. Can you elaborate on that?"
Build nodded, gathering his thoughts. He had spent the sleepless hours of the previous night thinking about how to explain his situation, and he had come to the conclusion that honesty was probably the best approach. These were superheroes. They dealt with weird stuff all the time. Parallel universes and alternate dimensions were practically Tuesday for these people.
"In my original universe," he began, "I was an ordinary human. No powers, no special abilities, just a regular guy living a regular life. I was... let's say 'enthusiastic' about a particular form of entertainment. A franchise called Kamen Rider."
He paused, trying to gauge their reactions. Most of them seemed politely attentive. Damian looked bored. Batman's expression remained unreadable.
"Kamen Rider is a long-running series about heroes who use belts called Drivers to transform into armored warriors. Each generation of the series features a different Rider with different powers and themes. The one I was most passionate about was Kamen Rider Build—a hero who used the power of science to fight evil."
He tapped the Build Driver on his waist.
"I died. I got hit by a truck. Classic isekai scenario, if you're familiar with that genre. And when I woke up, I was here—in this world, in a new body, with the actual Build Driver attached to me. Not a replica. Not a toy. The real thing, with all the powers it implies."
"Isekai?" The Flash asked, pronouncing the word carefully. "What's that?"
"It's a genre of Japanese fiction where the protagonist is transported to another world, usually after dying. Truck-kun is a common trope—getting hit by a truck specifically. I always thought it was ridiculous. Turns out it's apparently a real thing that actually happens."
"You're saying," Hal Jordan said slowly, "that you died in your universe, and some cosmic force decided to resurrect you in our universe with the powers of a fictional character from your original world?"
"That's the short version, yes."
"That's insane."
"Also yes. But here I am. And the powers are definitely real. You saw the footage from last night, right? The fight with Inferno at STAR Labs?"
"We saw it," Batman confirmed. "Multiple transformation states. Energy projection. Enhanced physical capabilities. Resistance to extreme heat. And a finishing move that generated enough kinetic force to register on seismic equipment three blocks away."
"That was a pretty light hit, actually. I was holding back because I wasn't sure how durable the guy was. Didn't want to kill him."
"How strong are you?" Superman asked. "At full power?"
Build considered the question. He had spent a lot of time thinking about this, comparing Build's feats in the show to what he had demonstrated so far. The answer was complicated.
"It depends on the form," he said. "The Build Driver uses FullBottles—containers that hold the essence of different concepts and objects. When I combine two compatible bottles, I get what's called a Best Match, which is more powerful than using incompatible bottles. Different Best Matches have different abilities and power levels."
He reached for his bottle carrier and pulled out the RabbitTank bottles.
"RabbitTank is the basic form. It's balanced—good speed from the Rabbit side, good power from the Tank side. Roughly equivalent to... maybe a mid-tier metahuman? I could probably fight someone like Sportsmaster or Cheshire and win without too much trouble."
He swapped the bottles for different ones.
"But I have access to more powerful combinations. KeyDragon, for example, combines the unlocking potential of a key with the raw power of a dragon. PhoenixRobo combines immortal flame with mechanical precision. And then there are the advanced forms—Hazard, RabbitRabbit, TankTank, Genius..."
"How advanced are we talking?" Cyborg asked, his mechanical eye whirring as it recorded everything.
Build smiled inside his helmet. This was the part he had been waiting for.
"In my original universe's fiction, Build fought and defeated a Rider called Decade—a being who could become any other Rider and had destroyed multiple worlds. Build also fused with Zi-O, the King of Time, to fight a threat that endangered all of reality. And Build's ultimate form, Genius, operates on a level of scientific understanding that borders on the metaphysical."
He let that sink in.
"So to answer your question: at full power, I'm probably one of the strongest beings you've ever encountered. Maybe not quite Superman-level—Kryptonian physiology is broken—but definitely in the upper tiers."
There was a moment of silence around the table.
"That's a bold claim," Aquaman said, his voice carrying the skepticism of someone who had seen many bold claims fail to materialize.
"It's not a claim. It's a fact. I can demonstrate if you'd like."
"Perhaps later," Wonder Woman interjected. "For now, let's focus on the more immediate concerns. You've been operating in Gotham City without authorization. While Batman has indicated that your actions have been helpful, we need to establish protocols. Guidelines. An understanding of how you'll operate going forward."
"I'm open to suggestions," Build said. "I don't want to step on anyone's toes. But I'm also not going to stand by while people are in danger. That's not negotiable."
"No one is asking you to," Superman said. "But working with the League has its advantages. Resources. Information. Backup when you need it. If you're going to be a hero in this world, it would be better to be an allied hero than a lone wolf."
Build nodded. This was exactly what he had been hoping to hear.
"I'd like that. I'd like that a lot, actually. Being a hero is... it's what I've always wanted. Not just the powers, but the opportunity to actually help people. To make a difference. If the Justice League is willing to have me, I'm willing to work with you."
"We'll need to run some tests first," Batman said. "Verify your capabilities. Assess your combat skills. Determine if you're actually as powerful as you claim."
"Fair enough. When do we start?"
Batman almost smiled. Almost.
"Now."
The testing facility was located beneath the building, accessible via a secret elevator that required biometric scans from no fewer than three Justice League members to operate. Build was impressed by the paranoia. He was also slightly terrified by it.
The facility itself was enormous—a vast underground complex that stretched for what felt like miles in every direction. There were training rooms and laboratories and holding cells and medical bays and approximately eight thousand other things that Build didn't have time to examine because Batman was walking very fast and everyone else was following.
They ended up in what could only be described as an arena. It was circular, roughly the size of a football field, with reinforced walls that looked like they could withstand a nuclear blast. Observation windows lined the upper level, and Build could see technical equipment being operated by League support staff.
"This is where we evaluate new metahumans and prospective members," Wonder Woman explained. "The walls are reinforced with Nth metal alloys and Apokoliptian technology. They can withstand most forms of physical damage."
"Most forms?" Build asked.
"Superman has broken them twice. But he was under mind control both times, so it doesn't really count."
"Cool. Cool cool cool. That's not terrifying at all."
Damian stepped forward, and Build noticed that the brat had changed into a different Robin costume—more armored, more tactical, designed for actual combat rather than stealth or agility.
"I'll go first," Damian announced. "I want to see if this 'Kamen Rider' is as capable as he claims."
Build looked at the twelve-year-old assassin with an expression of absolute delight that was entirely hidden by his untransformed face.
"You want to fight me?" he asked.
"I want to test you. There's a difference."
"Is there? Because it sounds like you want to fight me. Which is adorable. Really. The confidence is impressive for someone so short."
Damian's eye twitched. "I have defeated opponents far more dangerous than you. I have trained with the League of Assassins since I could walk. I have—"
"Been humbled by literally everyone you've ever fought the first time you fought them," Build interrupted. "Dick Grayson beat you. Tim Drake beat you. Jason Todd beat you. Cassandra Cain beat you so badly you probably still have nightmares about it. Maya Ducard beat you. Colin Wilkes beat you. Jon Kent has beaten you multiple times, and he's younger than you."
He started counting on his fingers.
"Deathstroke has beaten you. Ra's al Ghul has beaten you—multiple times. Talia has beaten you when she was mad at you. The Court of Owls nearly killed you. Goliath the dragon-bat had to save your life on at least three separate occasions. And don't even get me started on the number of times your father has had to pull your arrogant ass out of the fire because you overestimated yourself and underestimated your opponent."
The room had gone very quiet.
Damian's face was an interesting shade of red. His hands were clenched at his sides, trembling with barely-suppressed rage. Behind him, Dick Grayson—who had apparently arrived at some point without Build noticing—was trying very hard not to laugh.
"How do you know all of that?" Batman asked, his voice dangerously quiet.
"I told you. In my universe, you're all fictional characters. I've read the comics. I've watched the movies. I've seen the cartoons. I know everything that's been published about all of you—your origins, your powers, your weaknesses, your greatest victories, and your most embarrassing defeats."
He pointed at Damian.
"I know that he's arrogant because he was raised to believe he was destined for greatness. I know that he struggles with empathy because the League of Assassins doesn't exactly encourage emotional development. I know that he's gotten better over the years—marginally—but he still has a fundamental problem with respecting anyone he perceives as beneath him. Which, in his mind, is almost everyone."
Damian lunged.
It was fast—faster than any twelve-year-old should have been able to move, a testament to his assassin training and the physical conditioning that had been drilled into him since birth. He crossed the distance between them in a fraction of a second, a knife appearing in his hand from somewhere, the blade aimed at Build's throat with lethal precision.
Build didn't move.
The knife stopped an inch from his neck, held in place by Damian's own decision not to actually kill him in front of the entire Justice League. But the intent had been there. The willingness to do harm.
"You talk too much," Damian hissed.
Build smiled.
"And you're still short."
He grabbed Damian's wrist, twisted, and threw.
The movement was smooth and practiced, drawn from a dozen different martial arts that Build had never actually studied but somehow knew anyway. Damian flew through the air, his assassin training allowing him to twist and land on his feet instead of his face—but the surprise was evident in his expression.
"How—"
Build reached for the Build Driver.
"Let me show you something," he said. "Since you're so eager to test me."
He inserted two FullBottles into the Driver.
GORILLA! DIAMOND!
He cranked the lever.
KAGAYAKI NO DESTROYER! GORILLAMOND!
The transformation washed over him in a cascade of mathematical formulae and scientific notation. When it cleared, he was armored in a new Best Match—the left side covered in brown, simian-themed armor with oversized gauntlets designed for devastating punches, the right side gleaming with crystalline diamond plating that refracted light into rainbow patterns.
Damian attacked again, because of course he did. The brat had never learned to quit while he was ahead.
Build caught the incoming punch with his Diamond hand, the crystalline surface completely absorbing the impact. Damian tried to pull away, but Build's Gorilla fingers closed around his fist with the strength of an angry primate.
"GorillaMond," Build explained conversationally while Damian struggled to escape. "Gorilla for strength, Diamond for hardness. It's not my most powerful form, but it's more than enough for dealing with an arrogant child who thinks assassin training makes him invincible."
He lifted Damian off the ground with one hand.
"Let me explain something to you, Robin. I know your entire history. I know every fight you've ever been in, every opponent you've ever faced, every technique you've ever used. I know your fighting style better than you do. I know your weaknesses better than you do. And I have the power to exploit every single one of them."
He set Damian down—gently, because he wasn't actually trying to hurt the kid, just humble him—and released his grip.
"So here's some free advice: lose the attitude. Learn some humility. Treat the people around you with respect. Because one day, you're going to run into someone who knows everything I know and doesn't have my restraint. And on that day, your arrogance is going to get you killed."
Damian stared at him, his expression a complicated mixture of fury and something that might have been the beginning of self-reflection.
Probably not, though. Damian Wayne was not known for self-reflection.
"This isn't over," Damian said.
"It really is," Build replied. "But feel free to try again whenever you want. I can do this all day. I have, like, forty different Best Matches."
He didn't actually know if he had forty Best Matches. He hadn't counted. But it sounded impressive.
Dick Grayson finally stopped trying to hide his laughter.
"I like this guy," the original Robin said, walking over to pat Build on the shoulder. "Anyone who can put Damian in his place is okay in my book."
"Grayson—" Damian started.
"What? He made valid points. You are arrogant. You do underestimate people. And apparently, you have been beaten by literally everyone at least once."
"That's not—I have grown since then—Father, tell him—"
Batman's expression remained completely neutral. "He's not wrong, Damian."
The sound that emerged from Damian Wayne's throat was something between a growl and a scream. He turned and stormed out of the arena, his cape billowing behind him with maximum dramatic effect.
Build watched him go with a sense of deep satisfaction.
"That was incredibly cathartic," he said. "I've been waiting to do that for years."
"You mentioned that you know our histories," Superman said, his tone thoughtful rather than accusatory. "Does that include our weaknesses?"
"Yes. But don't worry—I'm not going to share them with anyone or exploit them myself. I'm a hero, not a villain. I'm on your side."
"And if you weren't?"
Build considered the question seriously.
"If I weren't, you'd probably be in trouble. But you'd figure it out eventually. You always do. That's kind of your thing—being the Justice League and all."
Superman nodded slowly, apparently satisfied with the answer.
"Shall we continue the testing?" Wonder Woman asked. "I believe we were interrupted before we could properly evaluate your combat capabilities."
Build grinned inside his helmet.
"Absolutely. Who's next?"
The testing lasted for several hours.
Build fought training drones and combat simulations and holographic recreations of famous villains. He demonstrated RabbitTank's speed and power. He showed off GorillaMond's raw strength. He cycled through NinNinComic—a Best Match that combined ninja stealth with the reality-warping power of comic book physics—and used it to literally walk through walls while the League's sensors tried and failed to track him.
He transformed into HawkGatling, soaring through the arena's vast open space while raining down a barrage of energy bullets on targets below. He became OctopusLight, using the combination of flexible tentacle-like appendages and hard-light projections to simultaneously engage eight different opponents. He shifted to RocketPanda, which combined the explosive propulsion of rocket technology with the surprisingly effective combat capabilities of a bear-themed warrior.
Each transformation revealed new abilities. Each Best Match demonstrated a different approach to combat. The League watched with increasing amazement as Build cycled through forms that shouldn't have been possible, each one more specialized and more powerful than the last.
"The energy readings are off the charts," Cyborg reported from the observation booth. "Each transformation involves a complete molecular restructuring of the armor components. It's not just changing appearances—it's fundamentally altering the physical properties of the suit."
"How is that possible?" Batman asked.
"I have no idea. The science doesn't make sense by any framework I'm familiar with. It's like... like the laws of physics are being rewritten in real-time to accommodate whatever he needs."
"That's exactly what it is," Build called up to them, having overheard the conversation through his helmet's enhanced audio systems. "The FullBottles contain the essence of their respective concepts. When I combine them, I'm creating a new formula—a new law of physics that applies specifically to me and my armor. It's not magic, exactly, but it's also not conventional science. It's somewhere in between."
"That's terrifying," the Flash said.
"It's awesome," Build corrected. "There's a difference."
The final test of the day was a sparring match with Wonder Woman.
Build had been looking forward to this one. Not because he thought he could win—Diana was one of the most skilled warriors in history, with thousands of years of combat experience and the blessings of actual gods—but because fighting an Amazonian warrior princess was the kind of experience that his previous life could never have offered.
He transformed into his most combat-focused Best Match for the occasion.
DRAGON! LOCK!
SHOURI NO RULE! KEYDRAGON!
The KeyDragon form was elegant and powerful, combining the unlocking potential of key-based technology with the raw draconic energy of mythological beasts. The left side of his armor was silver and mechanical, featuring key-like protrusions and locking mechanisms. The right side was red and scaled, with dragon motifs and a helmet that featured prominent horns.
"Interesting choice," Wonder Woman said, drawing her sword and shield. "Are you ready?"
"Are YOU ready?" Build countered, because the catchphrase was important. "Because the laws of victory have been decided!"
Diana smiled—a warrior's smile, full of anticipation and respect.
"Show me."
She moved first, crossing the distance between them with speed that Build's eyes could barely follow. Her sword swept toward him in an arc that would have bisected an ordinary opponent, the blade gleaming with divine enchantment.
Build parried with his arm, the Key-side armor generating a barrier of interlocking mechanisms that caught and held the sword in place. Diana's eyes widened slightly—this was apparently not a common occurrence—and Build took advantage of her surprise to counterstrike.
His Dragon-side arm swept forward, trailing crimson energy that coalesced into a claw of pure draconic power. The strike connected with Diana's shield, and the impact sent shockwaves rippling through the arena.
Diana held her ground. Of course she did. She was Wonder Woman.
But she also grinned, and Build knew that he had earned her respect.
The fight that followed was intense, beautiful, and absolutely one-sided in Diana's favor.
She was simply too good. Too experienced. Too skilled. Every technique Build tried, she countered. Every attack he launched, she deflected. Every opening he thought he found was revealed to be a trap, a feint, a deliberate vulnerability designed to lure him into overextending.
He lasted four minutes before she disarmed him—literally, removing his Dragon-side gauntlet with a precise strike that exploited a gap in his armor's coverage—and pinned him to the ground with her boot on his chest.
"Yield?" she asked.
"I yield," Build agreed, because he was not stupid. "That was incredible. You're incredible. I think I'm in love."
Diana laughed and helped him to his feet.
"You fight well for someone with no formal training. Your instincts are good, and your adaptability is impressive. With practice, you could become a truly formidable warrior."
"High praise from an Amazonian princess. I'll take it."
He detransformed, the armor dissolving back into the Driver as his human form reasserted itself. Around him, the League members who had been observing applauded—some genuinely, some politely.
"Impressive," Superman said, flying down from the observation booth. "Very impressive. I think we've seen enough. Batman?"
The Dark Knight nodded once, the closest thing to approval Build had yet received from him.
"He's legitimate. His powers are real. His intentions appear genuine. I recommend provisional membership, with continued monitoring until we're confident he poses no threat."
"Agreed," Wonder Woman said.
"Seconded," the Flash added.
One by one, the League members voiced their agreement. Even Aquaman, who had looked skeptical throughout the testing, offered a grudging nod of acceptance.
"Welcome to the Justice League," Superman said, extending his hand. "Provisionally."
Build shook it, marveling at the fact that he was touching Superman's hand with his own hand and that was a thing that was actually happening in his life.
"Thank you," he said. "I won't let you down."
The celebration of Build's provisional acceptance into the Justice League was interrupted by an alert.
Red lights flashed. Sirens wailed. The screens on the walls shifted from their normal displays to emergency broadcasts showing chaos in the streets of Gotham City.
"What's happening?" Build asked.
"Joker," Batman said, his voice going flat and cold in a way that suggested deep personal investment in the situation. "He's escaped from Arkham again. Reports indicate he's taken hostages at the Gotham City Convention Center."
Build's eyes widened.
The Joker.
The Clown Prince of Crime.
The most infamous villain in the entire DC Universe, responsible for more death and suffering than almost any other individual on the planet. The man who had killed Jason Todd, paralyzed Barbara Gordon, tortured countless innocents, and generally made Gotham City a worse place to live through sheer force of malevolent personality.
Build hated the Joker almost as much as he hated Damian Wayne. More, actually, because at least Damian had the excuse of being raised by assassins. The Joker was just evil for the sake of being evil, a monster in clown makeup who thought murder was comedy.
"I'm coming with you," Build said.
Batman looked at him, and for a moment, Build thought he was going to refuse. The Joker was Batman's nemesis. His responsibility. His burden to bear.
But then Batman nodded.
"Stay close. Follow my lead. And whatever you do, don't underestimate him."
"I won't," Build promised.
He had read enough comics to know that underestimating the Joker was a fatal mistake.
The Gotham City Convention Center was surrounded by police when they arrived.
Commissioner Gordon was on scene, looking tired and frustrated in the way that only years of dealing with Gotham's criminal element could produce. His officers had established a perimeter, but they were clearly outmatched—the Joker had hostages, and the Joker had leverage, and the Joker had absolutely no regard for human life.
Batman landed beside Gordon in a swirl of cape and shadow. Build landed beside Batman in a slightly less dramatic fashion, his RabbitTank armor gleaming under the emergency lights.
"Status?" Batman asked.
"Forty-seven hostages, including a school group that was visiting the comic convention happening inside. Joker has them in the main exhibition hall. He's demanding the usual—Batman's head on a plate, a helicopter to the airport, a billion dollars in unmarked bills, a pony. The pony is new."
"Demands?"
"Mostly for show. We both know what he really wants."
"Me."
"You."
Batman's jaw tightened. "I'm going in."
"I'm going with you," Build said.
Both Batman and Gordon turned to look at him.
"Who's this?" Gordon asked.
"New ally. Provisional Justice League member. He's been vetted."
"Is that armor?"
"It's complicated."
Gordon looked like he wanted to ask more questions, but the screams coming from inside the convention center made the urgency of the situation clear.
"Just don't let anyone die," he said.
The inside of the convention center was a nightmare.
The Joker had been busy. Bodies of security guards lay scattered near the entrances, their faces frozen in the rictus grins that were the signature of Joker toxin. Laughing gas canisters were positioned throughout the main hall, ready to be triggered at a moment's notice. And in the center of the chaos, surrounded by terrified hostages and grinning henchmen, stood the Clown Prince of Crime himself.
He was exactly as Build had always imagined—tall and thin, with chalk-white skin and green hair and a red-lipped smile that stretched too wide to be natural. His purple suit was immaculate despite the violence around him, and his eyes... his eyes were the worst part. They held no sanity. No empathy. No connection to normal human emotion.
"Batsy!" the Joker crowed as Batman emerged from the shadows. "You came! I knew you would! You always do! It's what I love most about our relationship—the reliability!"
Batman said nothing. His fists clenched at his sides.
"And you brought a friend! How delightful!" The Joker's attention shifted to Build, taking in the armored form with exaggerated curiosity. "Now what are you supposed to be? Some kind of robot? A Power Ranger? Ooh, are you one of those Japanese heroes? I love Japanese culture! The artistry! The precision! The total disregard for Western safety standards!"
Build stepped forward.
"Kamen Rider Build," he said. "And I'm going to give you exactly one chance to surrender before I end this."
The Joker burst into laughter.
"Surrender? SURRENDER? Oh, that's rich! That's absolutely hilarious! Do you know who I am, you walking action figure? I'm the Joker! I don't surrender! I don't negotiate! I don't—"
Build moved.
The RabbitTank form's speed was more than enough to cross the distance between them before the Joker could finish his sentence. Build's fist connected with the clown's face, and the Joker went flying backward, crashing through a display booth and into a wall with enough force to crater the drywall.
The henchmen reacted immediately, raising their weapons, preparing to fire. But Build was faster than all of them. He became a blur of red and blue, moving through their ranks like a force of nature. Punches landed with Tank-powered precision. Kicks swept legs and shattered weapons. Bodies flew through the air and crashed to the ground, unconscious before they knew what hit them.
It took approximately eight seconds to incapacitate every henchman in the room.
Build turned back to the Joker, who was pulling himself out of the wall with a dazed expression.
"That... that wasn't in the script," the clown muttered. "You weren't supposed to actually hit me. Nobody actually hits me. They monologue. They negotiate. They give me time to escape. That's how this works."
Build walked toward him.
"New rules," he said. "I'm not from around here. I don't play by your games. And I really, really don't like you."
The Joker's hand went to his pocket, pulling out a small device—probably a trigger for the laughing gas canisters. But Build was already there, grabbing the clown's wrist and squeezing until bones creaked and the device clattered to the floor.
"No," Build said.
"Do you have any idea how many of these scenarios I've planned?" the Joker hissed, his smile finally faltering. "How many contingencies? How many—"
"Do you have any idea how little I care?"
Build lifted the Joker off the ground with one hand, holding him at arm's length like a piece of garbage.
"In my universe, you're a fictional character. A villain. A monster who exists to be defeated by heroes over and over again. You have no power over me. You have no psychological leverage. You're not scary to me—you're pathetic. A clown who thinks he's important."
He threw the Joker to the ground at Batman's feet.
"There. I gift-wrapped him for you. You're welcome."
Batman stared at the groaning form of his nemesis, then looked up at Build with an expression that was almost impossible to read.
"That was... efficient," he said finally.
"That was cathartic," Build corrected. "I've been wanting to punch him since I was twelve years old. The comics. The movies. The animated series. Every time he got away, every time he hurt someone, I wished someone would just end it. Well, now I'm here, and I have the power."
He looked down at the Joker, who was trying to crawl away.
"And I'm going to make sure he never hurts anyone again."
"Build—"
"I'm not going to kill him," Build said quickly, reading the concern in Batman's voice. "I know that's your rule. I respect it. But I'm going to make sure Arkham actually holds him this time. I'll design a containment system myself. Use the science of the FullBottles. Create something he can't escape from."
Batman was silent for a long moment.
"We'll discuss it later," he said finally. "For now, let's focus on the hostages."
The hostages were freed. The police moved in. The Joker was taken into custody, still muttering about how the whole thing was unfair and how Build had cheated by not following the established dramatic conventions.
Build ignored him.
As he stood outside the convention center, watching the ambulances arrive and the hostages reunite with their families, he felt something he had never experienced in his previous life:
Purpose.
This was what he was meant to do. This was why he had been given the Build Driver, the FullBottles, the power to transform. Not just to fight villains, but to protect people. To save lives. To be the hero he had always wanted to be.
And he was just getting started.
Later that night, back at the provisional quarters the League had provided for him, Build lay on his bed and stared at the ceiling.
The day had been exhausting. Meeting the Justice League. Humbling Damian Wayne. Fighting Wonder Woman. One-shotting the Joker. It was more excitement than his previous life had contained in its entirety, compressed into a single twelve-hour period.
But his mind was still active, still spinning with possibilities.
He had demonstrated several Best Matches today. RabbitTank. GorillaMond. KeyDragon. NinNinComic. HawkGatling. OctopusLight. RocketPanda. Each one had been powerful, useful, effective in its own way.
But there was more. So much more.
He thought about the advanced forms. RabbitRabbit, which doubled down on speed to create something almost impossibly fast. TankTank, which doubled down on power to create something almost impossibly strong. Hazard, which increased all stats at the cost of control and sanity.
And Genius.
Genius Form was the pinnacle of Build's power in the show. It used all sixty FullBottles simultaneously, granting access to every ability Build had ever demonstrated plus some that defied explanation. The suit was covered in the periodic table of elements, a visual representation of mastering all of science.
Could he achieve Genius Form? Did he have access to all the bottles he would need?
And then there were the fusion forms.
In the show, Build had fused with other Riders on several occasions. The most famous was the fusion with Zi-O, creating a hybrid form that combined Build's scientific mastery with Zi-O's temporal powers. That fusion had been powerful enough to threaten reality itself.
Could he fuse with anyone here?
The thought was intriguing. What would a fusion with Superman look like? Would the FullBottles be able to contain Kryptonian essence? What about the Speed Force—could the Flash's power be bottled and combined with something else?
What about magic users? The DC Universe was full of mystical power—Doctor Fate, Zatanna, Constantine, the Spectre. Could the Build Driver interface with magic, or was it purely scientific in nature?
And the cosmic entities. The New Gods. Darkseid. The Anti-Monitor. The Endless.
Build's mind raced with possibilities.
He needed to experiment. Needed to test. Needed to push the limits of what the Build Driver could do and discover where those limits actually were.
But that could wait for tomorrow. Tonight, he was tired.
He closed his eyes and let sleep take him, dreaming of equations and transformations and a future full of heroic possibilities.
Tomorrow, the experiments would begin.
To Be Continued...