Ten years have passed since the Skywall Incident, in which Japan was split into three countries: Touto, Seito, and Hokuto. I, the brilliant physicist, Sento Kiryu, fought against the extraterrestrial entity known as Evolt, who wanted to destroy the Earth and absorb its energy into his own! Along the way, I met the muscle brained idiot, Ryuga Banjou, a wrongfully convicted fighter, Kazumi Sawatari, a farmer who wanted nothing more than to meet his idol, and Gentoku Himuro, a man seeking redemption for the harm he caused to the world.

All of us together transformed into the Kamen Riders, heroes of justice who wanted the same goal: to protect the Earth from Evolt’s hands. Despite our best efforts, we lost Kazumi and Gen-san to Evolt’s hands. In the end, I was left alone to battle Evolt. Without my most powerful form, Genius, I was forced to use Banjou and I’s final power, RabbitDragon, the ultimate Best Match. The worlds properly fused… but now I find myself alone in a field. Is this… the new world?

Pandora’s Box, which contains enough energy to destroy the Earth, has finally been opened! Standing up to Evolt, the extraterrestrial life form that has gained its power, are the Kamen Riders!

Sento sat alone, staring up at the beautiful sky before him. It was everlasting, and to him a testament to what he had done. Evolt had been defeated, permanently, and now there was a whole new world before him. But… he was alone. Banjou… Kazumi… Gen-san… Misora… Sawa-san… It was very likely he would never see them again. He sighed a bit and got up to his feet.

“A brand new world, huh?” Sento said to himself, still staring up to the sky. He looked ahead, a brand new path before him.

“This is the world you created, isn’t it?” Takumi Katsuragi asked, appearing from deep within Sento. He stared outward. “I was always so deep in my science, that I never could appreciate the true beauty of the world. You did a fantastic job eliminating Evolt… However, that sacrifice means you are alone in this world. And everything you’ve done will be forgotten.”

Takumi Katsuragi… The only person that Sento knew in this world. He was Sento’s original personality before Evolt erased him from existence and replaced him with Sento. Now the two shared one body, and Takumi rarely came out to speak. The two were one now. Sento bent over and picked up the White Pandora Panel, which had miraculously survived the attack and had landed in his possession, apparently. A victory in and of itself.

“This world, eh? I should probably find out where I am though… This field doesn’t seem familiar at all.” Sento ran a hand through his hair, walking forward through the field and onto an old path. He walked along it, thinking about this brand new world… One that wouldn’t require the Rider System or Project Build. “This is fantastic…! Although… The fact remains that I don’t exist in this world. Is it my reward…? Or my curse?”

“A curse for both of us, no doubt. This world will no longer require the protection of the Kamen Riders, now that Evolt and the rest of the Blood Tribe has been eliminated.” Katsuragi said, musing on the fact that his horrible project no longer needed to be used. Build was a powerful weapon, and it no longer needed to be used.

“Evolt… is gone. Everything is gone now… How sad.” Sento replied, sighing a little bit. He would miss his friends, that’s for sure. If not for them, all fighting for love and peace, then the world would have never been saved. He put his hands into his pocket and removed the Rabbit and Tank Fullbottles from it. A smile appeared on his face. “But if there is ever another threat… Build will be there to protect the people from harm.”

Takumi nodded, as he looked around, utilizing Sento’s perception and senses. The Devil’s Scientist looked, seeing a sign before them.

“A sign? Looks kind of old fashioned though, is it made of wood?” Sento asked, also noticing the sign. The man walked up to the sign, the language, at first, unreadable to him. “What’s this language…? I can’t make it out.” Suddenly, the White Pandora Panel began to glow a brilliant white color. Soon enough, the language began to reconstruct itself to where it was readable now. It was a two-way sign, one arrow pointing to somewhere called the Everfree Forest, and the other pointing to a place called Ponyville.

This had to be a joke, right? A fine name for a forest, sure, but Ponyville? Would anyone actually name a place that? It had to be an elaborate joke being played on misfortunate travelers.

“A joke, right?” Sento asked himself.

“It has to be. Nowhere on Earth would there be place called Ponyville. It makes no sense, at all, does it?” Katsuragi replied, closing his eyes for a moment. “However, the only logical next step is to head to this place. There has to be some answers there.”

“Yeah, you’re right. Let’s go.” Sento said, as Katsuragi disappeared back within him. He ran as fast as he could, down the path, and towards this Ponyville. The nature around him was unnatural to him. He lived so long in the city, that he didn’t know what this kind of lush nature was really like. He made a mental note to check out this Everfree Forest when he had the chance.

The road continued for quite some time, before over a hill, he could see his destination. What he saw was… not a city. It was a small little village, with wooden houses. Far different from the tall metal skyscrapers he was used to in Touto. Despite being quite a bit away, there was one thing he could hear. Yelling and screaming. It had to be a group effort if he were to be hearing it all the way from here.

“This can’t be good.” Sento said to himself, making his way down the hill and toward the village. Upon his arrival in said Ponyville, he was astounded to see… well just that. Ponies. They paid him no heed as they yelled and ran opposite of him. He wondered what it could all be about. Then he saw it, clear as day and standing just a few yards away from him. It was large, on hind feet, and looking to destroy.

“A Smash?” Sento asked himself, looking forward at the monster before him. It seemed to be a low level version, nowhere near the copied Lost Smash or Clone Smash that he had fought before. What was a Smash doing here though, especially since from what he gathered, this was no big city. This was a small village in the middle of nowhere, in a society that didn’t seem to have made the same scientific advancements as his own had done.

However, despite the fact that this world seemed impossible and was being inhabited by technicolor sentient ponies, he had to stop the Smash and save them. Despite just getting done saving the world from certain doom, he was already back to it. Wonderful, the scientist thought to himself. The Smash, making a groaning sound, looked at Sento.

“Sorry, I think I’m ready to deal with you now. So then, shall we begin the experiment?” Sento asked, attaching his Build Driver to his waist. He shook the red and blue Fullbottles he held, before inserting them into his Build Driver.

Rabbit! Tank! Best Match!

Are you Ready?!

“Transform!” Sento yelled, beginning to crank the lever on his Build Driver. The Snap Ride Builder appearing from within the belt, filling up the crystal clear tubes around him. It soon clasped on top of him, before returning to inside the belt.

The Fullmetal Moonsault! RabbitTank! Yeah!

“I’ve found the winning formula!” Kamen Rider Build, now fully transformed and striking his signature pose, said. He smiled, underneath his mask, and ran forward to strike at the Smash. The blow sent it flying backwards. It groaned loudly, as Build ran forward to fight it.

The Smash recovered from its fall, moving forward. It was a Strong Smash, as Build would classify it. Powerful with its strikes, but it had no special moves to pull off. Nothing more than a brute, an easy target for Build to defeat!

Summoning his Drill Crusher, a sword shaped to look like a drill, Build began to strike repeatedly at the monster. How easy was that? It had been a while since a fight had been so easy, and Build was happy to fight something so uselessly powerless.

The Smash got a few good punches in, but time after time of battling Evolt made Build realize how much weaker these attacks were. The Smash was clumsy and slow, its attacks doing nothing to faze Build’s posture.

Build didn’t realize, however, despite many of the ponies running away from the Smash, that one was watching him fight. And more than that, she was taking notes.

The Smash fell to the ground, this time not moving as much. It took a few moments for it to recover, getting back up from the ground. But by this point, Build had already one. Smiling, Build tossed the Drill Crusher to the ground, and began to crank the belt’s lever once more.

Ready, Go!

Build ran forward toward the Smash, a white energy chart appearing before him. He leaped onto the top of it, his leg sticking out, and began to follow the chart down, energy channeling into his foot. The Smash was trapped, and unable to move, with its final moments of consciousness being a foot gravitating toward its face.

Vortex Finish!

A small explosion occurred, and sent the Smash flying onto the ground, this time there was no recovering. Build ran forward and realized the Smash wasn’t transforming back.

“Oh that’s right… It’s been a while, hasn’t it?” Build said, searching around for a blank Fullbottle. Lucky for him, he had a couple to spare. He lifted it up and pointed it at the Smash, which began to have its power pulled away. Soon enough, the Smash returned to normal. Instead of a human face greeting him, however, there was another technicolor pony sitting before him, unconscious. She had a pale blue colored coat, and her mane was that of a rainbow, another thing that Build hadn’t seen much of before in Touto. She also had wings, making her a fictional character of legend, a Pegasus.

Where… was he again? Ponyville. That’s right. Makes a whole lot of sense to the rational thinking mind of Sento Kiryu.

Build pulled the Fullbottles out of his Driver, beginning to look around. He was unsure of where to go, or what to do. That’s when he turned around, to come face-to-face with another pony. This one was a purple color, with a variety of purplish colors in her mane. She had wings and a horn… he took mental notes on this one. A horn would make her a Unicorn, but at the same time, she had wings. What did that make her? Some hybrid of Unicorn and Pegasus?

There was an awkward silence between the two of them. Before the pony finally broke the silence.

“I have several questions for you. First off, one, what did you do to my friend?!” She sounded almost accusatory, as if Sento had been responsible for turning the blue colored pony into a Smash. He shook his head a bit, as he backed away. Her horn was glowing, and he knew that couldn’t be good.

“Ummm… I just saved her?”

“Saved her, huh?” Her horn stopped glowing, but she still looked a bit suspicious. “What are you, exactly? I’ve never seen anything like you before.”

“Me? Of course, you wouldn’t have heard of me, but I am the brilliant physicist Sento Kiryu!” He smiled a bit, always getting riled up when someone asked him who he was. He had a bit of an ego, but usually his friends… kept him in check. A frown appeared on his face.

“A scientist?!” Her ears perked up, and a smile appeared on her face for a flash second, before she shook her head a bit. “That can wait! You seem to be in the loop, though! What happened to my friend, Rainbow Dash? Will she be okay?”

Rainbow Dash, huh? Quite the literal name for a rainbow-maned flying pony. Sento turned around and looked at the unconscious pony. Sento nodded to the dual-wielding Unicorn/Pegasus pony.

“She should be fine. Your friend was turned into a creature known as a Smash. Where I come from that means she should have some memory loss of the time she was a Smash, and before that, but she should be fine otherwise. The pony had a sigh of relief as she walked toward the other rainbow pony and put her hoof on her friend. She was still breathing.

“That’s good to hear… But that still doesn’t explain what you are.” She pointed her hoof at Sento. “What are you exactly? And you said you’re a scientist?”

Sento shook his head a bit.

“Yeah that’s right. The most brilliant scientist to ever have lived!” Sento said, pulling off his signature pose. The pony sweat dropped a little. “But if you’re asking what I am, I am a human. Homo sapiens is the scientific name for our species. Hmm, that’s so odd. This world doesn’t seem to have our species in it. Rather, your kind is here! This is so interesting!” His hair had poofed up, and he excitedly ran his hands through his hair.

“Righttttttt.” She wasn’t exactly sure what this ‘human’ was talking about, but he seemed to know a thing or too about that monster. And not only that, but the armor he wore was what interested her the most. Rabbit and tank, she had heard the belt he wore announce. It was interesting, and she had to know more. “Oh! I’m so sorry, I haven’t introduced myself yet. I’m Twilight Sparkle, princess of friendship!” She had a sheepish grin.

“A princess? So this world still dabbles in royalty, very interesting indeed.” He was taking a multitude of mental notes. Twilight nodded to the human, before enveloping Rainbow Dash’s unconscious body in magic to lift her up. Sento wasn’t sure what this ‘magic’ was, but he was taking notes. Unicorns could use magic, he knew that much from the lore of his world, but he never expected to see it in action.

“Follow me, Mr. Sento. We can talk more at the Castle.” Twilight said, turning around and beginning to trot off toward another location. Sento nodded and followed behind the pony.

“You even have your own castle! This is so interesting!” Sento said, trying to keep his hair down, but unable. Twilight was suspicious of Sento, because she had never even heard of his species. Could he be native to the Everfree Forest? No, that couldn’t be it. He mentioned another world… That got her excited. Could there be a multitude of other worlds out there, ones that ponies had never heard of? If this being truly was from another world, her own scientific side might pop out. Two scientists blowing question after question toward each other? What could go wrong?

“Our first experiment… defeated? By whom?”

“We don’t know, boss… A masked creature in red and blue showed up out of nowhere and defeated it quickly! Not just that, but he was able to take the essence for himself!”

“Tch. Of course, some meddler coming into our plans just as we successfully create our first Smash. Even an Element of Harmony-made Smash was weak.”

“Her Hazard Level was nowhere near where it needed to be. We need a pony with a higher level before we can begin extracting essences for ourselves.”

“But if that masked creature gets in the way again… We may have no essence left for ourselves.”

“Don’t worry, we still have… our back up weapon.”

“Of course… How could I forget?”

The shadowy figure walked through the compound and walked up to the glass case on a pedestal. Inside it sat a Transteam Gun, and appropriately next to it was a manmade, purple and silver, Fullbottle. She smiled a bit as she broke open the case, grabbing the gun and bottle.

“With this… We’ll soon rule over all Equestria! Technology from another world is wonderful, isn’t it?” She said, looking over the gun. Another smile broke out over her face. It was a cruel smile. After shaking the Fullbottle, she inserted it into the Transteam Gun’s magazine-like rail system. The gun recognized the Fullbottle, and a symbol of a spider appeared on it.

SPIDER!

“Vaporize.”

Mist Match!

Spider Sp-Sp-Spider! Fire!

Mist appeared from outside the gun, covering the being in a dark shadowy haze. Firework likes sparks emanated from the armor and mist, as it soon evaporated. The armor was stark purple, with wire-like veins running all over it. A large purple spider was emblazoned on the front of the armor, its eight legs running on the torso of the suit. Heavy boots were fitted to her feet, and her gloves had sharp claws on the front. The helmet, too, was shaped like a spider, with a long horn protruding from the top of the helmet.

She stepped forward, raising her arms up toward the ceiling.

“Such power…! This is the power we will use to defeat the intruder! And then… all Equestria will bow down to us! Faust!” She announced to her followers, who raised their own arms up.

“For Faust!

Author's Note

Second attempt at submitting a fic here. This one requires knowledge of Kamen Rider Build to fully enjoy, but a short summary is in Sento's thoughts. Anyways, I hope you enjoy this story because I had a fun time writing it! Please enjoy and leave your thoughts/critiques! I'm more than happy to hear them!