I don't own Fairy Tail or Kamen rider Build.

Chapter 1 : Lets go to another world

/-Somewhere in Japan -/

Sun was just rising, and yet someone was coming, driving a quite strange red bike. In fact, it had a big toothed wheel on the front and what seems to be a kind of big yellow bottle coming out of the end. The driver was approching what looked like an old factory. He stopped just outside, pulled off his helmet and enter the building. After going down stairs for several minutes, he opened a door and was faced with a big, swirling blue wormhole, or at least it looked like one.

- "Ah, you are finally here, Sento Kiryu." said a voice

Turning to his right, Sento was now in front of the two men who called him here. The first one, the one who talked, was fully dressed in leather and quite old but you could see in his eyes that even if he was old, he could easily fight in more than one ways, and for good reason. His name was Takeshi Hongo, aka Kamen Rider Ichigo, the oldest of those warrior, and probably one of the most powerful. By his side was a young man dressed with a dark grey blazer, matching pants and shoes and a pink shirt. He also had an old red camera hanging around his neck. He was Tsukasa Kadoya, aka Kamen Rider Decade.

The young man, called Sento Kiryu, approached the two man, but without taking his eyes of the wormhole.

- "I tried to come as fast as possible, Takeshi, but now I know why" said Sento. "I'm sure its for this thing, isn't it ?"

- "To the point, as I see" noticed Tsukasa. "Well, you are right, that's the reason but it's just a …"

- "He isn't listening, Tsukasa" indicated Takeshi.

Tsukasa indeed noticed that Sento was litteraly all over the hole, a tuft of his hair high in the air from the excitation as he began to elaborate theories after theories. Takeshi didn't know what amused him the most : Sento's behavior or Tsukasa's facial expression.

- "KIRYU SENTO, ARE YOU LISTENING OR NOT ?! " shouted Tsukasa.

- "Eh ?", answered the physicist while turning back, remembering that he wasn't alone. "Oh, no need to explain anything to me. If you called me, it's necessarily for my genius. I am the only one who can truly understand what that thing is, isn't it ?"

- "We didn't call you here for your brain, Sento", answered Takeshi.

At that, Sento instantly calmed down, turning back again to the Riders, his tuft of hair falling back, as if it was deflated.

- "What ? But I'm here then ? ", asked the physicist.

- "If we say that this thing was created by Shocker, you will listening calmly ?", asked Tsukasa.

Sento lift his head up, then looked at the Riders straight into their eyes.

-"Tell me everything", asked Sento.

Takeshi then began to explain what was the situation.

- "A few weeks ago, we noticed that Shocker, even if they stayed in the shadow after their last defeat, were moving a lot more than before. I then asked many Riders, including Tsukasa, to discover where they were and when we found them, we were ready to surprised them. But as soon as we arrived, all of their troops, or at least a big part of it, jumped through this portal. We looked around for information and we found out that this thing is a portal to another world."

Sento's eyes widened at this revelation.

- « Another world ? What do you mean ? » asked the physicist.

- "We do not know much more unfortunately." Answered the photograph. "We know nothing about this world."

- "Well, we good let them there. I mean, we got rid of them, no ?"

- "If that was the case, we would have leaved this place already." Said Takeshi. "But Shocker didn't crossed this gate because we had them cornered : they were going to do it anyway. Which make me think that even if they don't know about this world, they wanted to go there and they probably have a way to come back."

- "And seeing you have one hell of a brain," continued Tsukasa "you can probably imagine what will happen if they come back here with a power from another world."

Indeed, Sento could perfectly see in his mind what kind of thing could happen with this scenario, and knowing Sento and his over-working brain, he probably was thinking about it A LOT.

- "Ok then, we can let them do what they want, but what can we do", he asked.

- "Simple : we send you there", answered Tsukasa

- "… Me ? In an unknow world ?", asked Sento, something strange starting to shine in his eyes.

- "Indeed, that's the best choice" nodded Takeshi. "We don't have what we need to build something that will help you to come back from there, but as a physicist, you, out of all the other Rider, have the best chance in finding a way home. It will be even easier since Shocker probably have a way to come back so if you can get the data from them, you'll be able to make your own way back. But it will be a dangerous journey. After all, we know nothing of the place you will be in and …".

- "He's not listening to you anymore, Takeshi", pointed out Tsukasa

Indeed, Sento had turned et was talking to himself, asking himself all the question he could think of about that world. You could hear "Is it a futuristic universe ? If that's the case, how advanced are they ? Are they more about mechanic ? or Chemistry ? Aaaah~, so many possibilities !" coming out of his mouth so fast you could barely understand what he was saying.

- "… Sento ?" asked Takeshi.

- "I'LL DO IT !", shouted Sento with enthusiasm.

- "OoooK, then I guess you can go prepare yourselves and come back tomorrow.", continued Tsukasa, still shocked by Sento's behavior.

- "OK" was the young man answer as he was speeding away.

The two Riders watched him leave, still surprised by the enthusiasm.

- "You…think he'll be fine ?", asked Decade to Ichigo

- "… Yes. I'm … sure we can trust him", answered Takeshi

Tsukasa, having noticed the hesitation in his comrade voice, looked to the portal, hoping everything will be fine.

/-Next morning-/

Sento came back to the warehouse the next day, but he wasn't alone this time. He was followed by Ryuga Banjou, aka Kamen Rider Cross-Z, Misora Isurugi and Sawa Takigawa, the three of them having insisted on accompanying him.

- "Why did you come again ?", asked Sento, clearly annoyed that they had convinced him to let them come.

- "To know exactly what you are getting yourself into, Baka", answered Misora

- "She's right. You really think we are gonna let you go who know where with ALL the Fullbottles, your Driver and even the Sparkling Bottle and the Hazard Trigger without any further explication ?", completed Ryuga. "And since you've been called by Ichigo and Decade, it must be something big."

- "I already told you what I'm gonna do.", countered Sento. "I'm going somewhere to fight bad guys".

- "THAT'S NOT AN EXPLANATION ! », shouted Ryuga

- "That's enough for someone with a brain like yours.", retorted Sento

- "I'M GONNA KILL YOU ? YOU LITTLE …"

- "Stop that now, it's neither the moment nor the place.", said Sawa trying to stop the boys.

- "Anyway, what's YOUR reason to come with us, Sawa ?", asked Misora to change the subject.

- "I'm gonna have an interview with those two Riders", she answered with confidence

Not expecting a reason so stupid and serious at the same time, the three other fell to the ground.

- "What ? Meeting two legendary Riders, it's gonna be the interview of my life !", telled Sawa with stars in her eyes.

- "Calm down now, we are here.", noticed the dragon Rider.

Indeed, they were at the door. Sawa straightened her clothes, check herself in her pocket mirror one last time before opening the door. What she saw behind it made her heartbeat skyrocket, but what she felt in the air made her feel uneasy.

The raise of her heartbeat because Decade and Ichigo weren't the only Riders here. All the Rider from the Neo-Heisei were here : Shotaro Hidari and Philip, Eiji Hino, Gentaro Kisaragi, Haruto Soma, Kouta Kazuraba, Shinnosuke Tomari, Takeru Tenkuji and Emu Hojo. It could be the interview of a lifetime for Sawa. But the air was heavy. They all had a frown on their faces, a sign that they were just denied something. When Ryuga saw the vortex, he asked :

- "What is that ? "

- " It's a portal to an unknow world.", answered Shotaro

- "What ? Really ?", asked Misora

- "Yeah, and Sento was chosen among all of us to go to this world, find Shocker and bring them back", completed Philip.

- "What ? And he is going alone ? Are you out of your mind ?", Asked Sawa with surprised and anger in her voice

- "Yeah, at least let me go with him.", demanded Ryuga.

- "We can't. None of us can.", answered Eiji

- "But why ?"

- "I'll never leave a buddy whose in a pinch." Affirmed Gentaro. "But the portal isn't strong enough."

- "It seems to have the energy to take just one person.", said Haruto "But we still have hopes that he will came back"

- "Sento is the most intelligent of all the Riders, if there is someone who can find a way to come back, even in a world he doesn't know, it's him." Said Kouta with conviction.

- "He might even be able to contact us with his Build Phone, so we could always help him if he need informations. We'll never be far away. " continued Shinnosuke.

- "Moreover, there is a great chance that this world might be inhabited and as a Kamen Rider, it will be his job to protect them from Shocker." Said Takeru.

- "To have fought by his side, I know that he'll succeed in all of his missions : finding Shocker and bringing them back", said Emu with high confidence.

After hearing the opinions of the other Riders, Sento's friends calmed down.

- "You better come back, you hear me ?" asked Ryuga

- "Loud and clear." Answered Sento. He then turned to Sawa and Misora, who hasn't said anything.

- "Don't worry, I'll came back in no time. After all, I'm the greatest genius ever, right ?", asked Sento.

The girls smiled a little, hearing Sento's typical narcism, and lift their head.

- "Yeah. ", they nodded at the same time.

- "Sento, it's time.", said Takeshi

At that, Sento put his bag full of his devices on his back, walked to the portal, then turned one last time, facing his friends and the Riders.

- "Be strong, and make the values of Kamen Riders shine strong, Sento Kiryu." Asked Ichigo. "Go and come back with victory, KAMEN RIDER BUILD ! »

Everyone then echoed that shout, with cheering of their own :

- "Make them count up their sins !", said Shotaro and Philip

- "May their greed be their fall !", said Eiji

- "Let our friendship follow us to the end of the universe !", said Gentaro

- "It's showtime and you're the star !", said Haruto

- "Let that be your stage, now !", said Kouta

- "Go on, at top gear !", said Shinnosuke

- "Your life is gonna burn bright !", said Takeru

- "You'll clear this with no continue !", said Emu

- "Come back quickly, Sento ! », said Ryuga, Misora and Sawa in one voice

Sento smiled at everyone then turned to the portal.

"Now, shall we begin the experiment ?", said Sento before jumping in the vortex.

I have many thing to say. First, English is not my first language so sorry if my English is not perfect. Second, it's my first story ever so please be understanding and you have remark about my work, please review to give me advice, but please no flame. I hope you'll have a good time anyway.

Next time : Sento arrive in a new world, but not like he hoped. Meanwhile, a cat found a strange bottle and a fated meeting will happen.