Note: This starts after Kamen Rider Build: Final Stage and before Episode 49 of the Build Series, The Tomorrow Build Will Create according to the Build Timeline. In the RWBY timeline, it starts before Episode 1 of RWBY, volume 1. Also, spoilers for the Kamen Rider Build Series ahead.

Prologue: The World that Cross-Z finds himself in

"W..What the..." Banjo groans, trying to get up. There is a single feeling threatening to overwhelm him right now, the pain being just as bad as when he'd been struck with a finisher by Evolt back then. What the hell happened? They were fighting Evolt then... right! They were forced to find the lost bottles to complete the merging of worlds, but also at the same time, causing Evolt to revive once more after he was defeated. A final struggle ended with them winning after Sento and he were forced to use the Cross-Z Build form once more, alongside Grease Blizzard and Prime Rogue for Kazumi and Gentoku respectively. Sure, it was one hell of a battle. That guy was one hell of a tough nut to kill, but at least they won, right? But where is he now?

"Sento?" He calls out weakly, as the feeling of pain finally begins to subside. No response. Wait. Is he in a forest? He notices the vast expense of lush green trees, slowly getting up. On the ground is the Dragon Evol-Bottle and the Dragon Full-bottle, which he picks up. Good. For some reason, his body is still on high alert, subconsciously, as if there is a threat that is around, besides Evolt. But what can possibly threaten him? The Cross-Z Magma Knuckle is on the floor as well as the Cross-Z Dragon. But no sign of his Build Driver. How is he supposed to transform then? He sighs in frustration as he pockets everything except for the Dragon Evol-Bottle and the Dragon Full-bottle.

His hearing picks up a low growl and his instincts as a fighter kick in, immediately shifting himself into a boxing stance while grasping each bottle in each hand. "Who's there?!" He shouts. Soon enough, the source of the growl reveals itself. What the hell? Banjo tries to figure out what he's looking at right now. It looks like a wolf, but the wolf-like creature is completely black, save for a white mask on its face with red markings on it. Then more low growls, as several other of the same creatures appear.

So, a fight, huh? Well, he's currently able to fight, for now, that much is for sure. His . His strength is something that he's always been proud of. Pair that with the boxing skills that he managed to train up from professional fighting and fighting as a Kamen Rider, it makes for quite possibly and dare he say it, a Best Match. "Come get some!" He roars. A creature leaps towards him, and he punches with an uppercut to its underside with a shout. "ORYA!" A blue burst appears, as the creature is knocked back. Another one pounces on him and he aims as the mask this time. "ORYA!" It shatters on impact, with the creature's body dissolving into nothing. So the mask is the weak point? Banjou grins. This should be easy. They may have the numbers advantage, but their attack patterns are quite easy to tell. The only weapons they have are their claws and razor sharp teeth, which he can dodge with ease.

"I feel unbeatable at this moment!" He declares as another of these creatures bites the dust. There's no way he's going to lose. Soon enough, he's shattered almost all of the masks, resulting in seven of those dead creatures, leaving only an eighth. This one seems slightly stronger than the others, with a bigger body than the other ones. Is it the alpha? "Come and get some!" The alpha pounces, and he dodges to the side before slamming his fist into the alpha's mask with a powerful left hook. The alpha is sent flying back, as cracks begin to form on the mask. Then it all shatters, as it dies with a small, pathetic whine. Easy. It was barely a walk in the park, compared to the Lost Smash and Evolt. Especially the latter, who had been such a powerful opponent. His instinct, however, still remains on guard, despite the fact that every enemy was gone. Then, in his mind, it clicks. "Who's there?!"

"That was quite the performance." Someone steps out from the shadows. A woman. Her features and attire are certainly not Japanese, and he has to admit, she's quite pretty for a foreigner. However, the manner that she speaks it is quite odd.

"Who are you?" And his voice sounds weird too. But it doesn't matter right now.

"I'm Professor Glynda Goodwitch, of Beacon Academy. Who are you? Where did you come from? And why do you have such severe injuries?" She sounds quite monotone as if she's used to this kind of thing.

Banjou sighs. "I'm Banjou Ryuga. As for where I'm from..." Then he realizes something. He might not be on Earth. His Earth got merged with another one, so where did he even end up? Time to pull a Sento. "I'm not sure. I don't remember too much. Maybe it'll come back to me later. For my injuries... I think I was fighting? Then I don't remember."

"So you're either amnesiac or PTSD?" He blinks at the two terms. What did that mean? Oh right, Sento's condition was the first one. The annoying guy did mention it a few times. But what about the other one?

"Yes, I think?" He hesitates. "So where are we?"

"We're in the Emerald Forest, not too far off from Beacon Academy. How did you e- Right." She mutters that last part to herself. "Come, I'll bring you back to the Academy to be treated since it doesn't look like you have Aura to heal yourself."

"What's Aura?" He instantly responds, having never actually heard of the term before.

"To put it simply, think of it as a manifestation of the soul. It acts as a shield and you can heal from it." She explains as they slowly make their way back to wherever this Beacon Academy is. Damm, that sounds nice. If they had that back when Evolt was fighting, it would have been so helpful. Evolt. That name brought nothing but rage to the forefront of his mind. It was because of Evolt that caused his fiancee to die. Evolt also forced Kazumi to use Grease Blizzard, extinguishing his life. Evolt killed Gentoku, who could have helped restore the country back then. It was because of that damm bastard that he'd been experimented on, and framed for murder. It was because of him that this entire thing happened. He unknowingly smashed his fist into the nearby tree, causing the said tree to collapse somehow. Right, he was still clutching the Dragon Evol-Bottle and Full-Bottle. "What are you doing?! Calm yourself at once!" She hisses, as if afraid of something.

A loud screech resounds, causing him to look up. It looks like another of those creatures, except this time it's a giant bird with a white face mask. It was probably big enough to rival the size of the cafe, maybe even slightly bigger. Since when could birds grow that big?! "What the act-"

"Look what you've done! You've attracted the Grimm with your negative emotions!" Wait, so those things were attracted by his anger and frustration? Damm, no time to think. He readies himself in a fighting stance, ready to fight. He sees trees being felled in front of him, and a scorpion-like Grimm, as she calls them, bursts out of the forest and into the clearing. "I can fight them, but I'm not sure if I can protect you until backup arrives. The Nevermore and the Deathstalker are worst possible opponents I could face. And they're probably a century old." She takes a riding crop out from the boot of her right leg?

"Damm, if only I had my Driver..."

"What does it look like?" He blinks. Did the lady manage to find it? "What. Does. It. Look. Like." She repeats herself, pausing after each word. Damm, she must be quite fed up or something to be like that.

"It's got a crank, and two slots to place these bottles in." He quickly identifies two unique traits of the Driver.

"Is it that thing?" She pulls out his Build Driver out of nowhere.

"Where the hell did you keep it, lady?" He's curious, he isn't going to lie. She doesn't have a pocket or anything behind her back, from the looks of it. He takes the Build Driver. Good. He can probably fight the aerial opponent with the Beat Closer. The Deathstalker, as she calls it, should be a piece of cake as well now.

"Don't ask. What do you need to do with it?" She sharply retorts. Damm.

"Stand back." He instructs, placing the Driver on his waist, the belt appearing and securing itself on his waist. Glynda moves back a few metres, looking somewhat unsure. Pulling out the Cross-Z Dragon, he keeps the Dragon Evoll-Bottle, opting to go with the Evol-Bottle. Shaking the bottle a few times, he twists the cap and pushes it into the Dragon, pushing up its head and tail, before pushing it down onto the Build Driver. "Cross-Z Dragon!" The familiar sound rings out from the driver.

He grasps the crank of the Build Driver a few times and tube structures begin to appear, forming what appears to be half of a body suit in front and behind him, with a dragon at the side thanks to the essence of the bottle. As the structures solidify, he shifts into a stance. "Are you ready?"

"HENSHIN!" He declares, shifts to a standing position. The two halves of the suit smash into him, before the dragon part swings to behind him, covering him. Steam is let out, as the belt makes another announcement. "Wake up Burning! Get Cross-Z Dragon! Yeah!"

"What is this?" Glynda at the side cannot help but be astonished. Odd, do they not know the existence of Kamen Riders?

"I feel unbeatable at this moment!" He declares, charging at the scorpion creature.

"Wait, what are you doing?" Glynda tries to move him with her telekinesis. It is successful for a moment, before he someone manages to shrug off her semblance. How? Still, she has little time to be distracted, as the Nevermore begins it's descent, swooping down on her. Then she hears a loud shout.

"ORYA!" He sends the Deathstalker flying with a single punch. "See, I'm fine. You don't have to try and hold me back or anything." He calls out to her. The lady had tried to use something to stop him, he could feel that much. But it clearly couldn't, since he broke through with ease. Meh, it doesn't matter. He's definitely going to wipe the floor with this scorpion creature. This thing's pretty weak when he's in his base form though, which is pretty surprising considering the fact that it's just his base form. Then again, he did beat up Night Rogue and Blood Stark with ease back then. He turns the crank a few times, causing the Beat Closer to form in front of him. He quickly channels the power of the Dragon Full-Bottle into the sword and pulls the handle once. "Special Tune! Hippare! Smash Slash!"

The sword is wreathed in flames , causing Glynda to once again take her eyes off her opponent and he charges at the scorpion thing, slashing through it as he runs past it. It cuts through the scorpion like butter, causing an explosion to happen. Damm, it was that weak? It couldn't even take a single finisher from the Beat Closer. Now for the bird.

Glynda appears to be somewhat struggling, as she is somehow uprooting trees and aiming them at the Nevermore while using her whip to hit it whenever it got close enough. However, her attacks do not seem to do much as the trees miss due to its flying speed. "Do you think you can keep that thing grounded for a bit?" He asks the blonde, who shakes her head. Alright then. It seems like he'll have to do another finisher attack. He turns the crank a few more times, summoning a blue and orange oriental style dragon to fly and stay on the spot behind him. "Ready, Go! Dragonic Finish!" He charges for a second, before leaping up and performing a roundhouse kick as the dragon shoots him with a blast of fire, propelling him into the sky and into the bird. For some reason, the bird chooses to fly towards him, an ear-piercing screech conveying its intent to kill him. For some reason, he feels like shouting a name for his attack. No time to think. "Rider Kick!" He roars, as his foot comes into contact with the bird's head.

Then it explodes into fire, as the bird is knocked down, being burnt while dissolving into nothingness. He drops back down to the ground, pulling out Cross-Z Dragon. "That was pretty easy." He calls out, as the suit dematerializes, revealing his still injured self. "Now, can I get that treatment that you spoke of?" She nods dumbly, leading the way back once more.

Beacon Academy, Office

"So, you're Banjou Ryuga? And you don't know where you're from?" He nods at the Headmaster's question. He'd been given a treatment whatever they called Aura healing, which was making use of aura to heal his injuries at a rapid pace, which was pretty sweet, not going to lie. Although, they'd found the Nebula Gas within his body, which he temporarily brushed it off saying it was harmless, even though the doctor said that although they did not know what it was, it was in such a high concentration that it should have been fatal. Well, gotta thank his Evolt genes for that, huh? Then he'd been asked to come here, and that's his current situation, currently talking to the headmaster of Beacon Academy.

"Yeah." Still, having to maintain the charade of not knowing is kind of hard.

"And you have quite sharp instincts as well as strength in spades even though you don't have your aura unlocked." He nods his head once more. "Well, I'm not too sure what to do with you. You see, your clothes indicate that you come from one of the four cities and not a village, yet I am unable to find any records of your name despite having sifted through the entire Vale database. The only other possible place would be Atlas, but I doubt they have your records too. So, are you willing to tell me about yourself?" Did the old man just see through his lie? Damm it, he has to make up something quick. "Or, it's entirely possible that you come from a more modern village that was destroyed."

"Yes. I've been traveling from place to place and I stole the clothes, so yeah." He fibs, somehow.

"Now. According to the report, you used some sort of belt device to transform. May I know about that?" So they don't have Kamen Riders? This is going to be...quite the issue to resolve.

"It was a gift from a friend. I don't know whether he's still alive or not." The words are the truth. He thinks of when Sento gave him the belt and the dragon back then, and what it took for him to transform. Good times, huh?

"I see. We all do what's necessary for survival. Now, I see that you are a pretty good hand to hand fighter."

"Yes. I used to fight a lot professionally. Why the sudden curiosity?" Banjou still doesn't see where this is going. The old man seems to be speaking in circles.

"Are you interested in teaching hand to hand combat? Our students tend to rely far too much on their own weapons and don't seem to consider the possibility that their weapons might be lost to them during combat." His eyes widen. It's quite the offer, to be honest. He'll be able to settle down in this new world pretty quickly and the school might pay a lot and even give him refuge, something that he urgently needs.

"Headmaster! What do you mean by this?" He hears Glynda protesting. It is probably natural for her to do so since she has seen firsthand what the person can do.

"I mean what I said. Our students rely far too much on their weapons. So, Mr Banjo. Will you accept our offer?" There's no point in turning it down.

"I will."

"Welcome to Beacon Academy, Professor Ryuga Banjo."

A/N: So guys, this is something that I've thought up of after finishing Kamen Rider Build and Kamen Rider Build NEW WORLD: Kamen Rider Cross-Z. It was a good KR series and the merging of worlds and Banjo and Sento not "belonging" to the new world gave me this idea. What if, the riders were rejected by that new world, so they were sent to one that doesn't reject them? And here we are, in RWBY because why not?

It's first of all, an idea that I think is better than using Decade as a bridge to the world(No hate to this idea, just that it's kind of overused). Admittedly, I'm using the hired into Beacon cliche, so yeah, sorry about this part. Secondly, it will be pretty funny to see how Sento and Banjo adapt to this world. So yeah. Oh and btw, the Build Riders are kind of overpowered in this world, if you ask me. Especially since Cross-Z's stats in his base form are already pretty strong. I mean, 27.6 tons of punching power, 33.7 tons of kicking power, able to jump higher than Sento's Rabbit Tank form? (Better than almost all of Drive's Type Tridoron form's stats btw) Yeah, you get the idea. They won't transform as much, but yeah. It's more of them adapting, although they will be fighting in the suits of course from time to time.

Also, my updating schedule's gonna be pretty weird from here on out. I might update a different story each time and I'm not sure when I'll be updating. Might take 2 weeks, a day or several months. So yeah, I hope you guys can actually stay patient because life's honestly tough and we all have our own.

Hoped you guys enjoyed this chapter and leave a review if you guys think that there's room for improvement or any requests that you want! Some requests will be considered. Feel free to PM me if you want. Absurd requests are obviously not allowed and dun flame. I am only an amateur at this shit.

On that note, peace out people!

322n

Songs: These are songs from Kamen Rider Build

Be The One(theme song)

Ready Go!(Theme for RabbitRabbit/TankTank)

Burning My Soul(Theme for Cross-Z Magma)

Evolution(Theme for Kamen Rider Evol)

Build Up(Theme for Genius)

Law of the Victory(Theme for when Build, Cross-Z, Grease and Rogue fight together).