Meanwhile in the Stein House

Seeing the young man is watching the new series of Kamen rider Saber on his laptop. He is currently watching the new episode.

His name is Sam Stein.

Sam: NANI?!?!?!?!? My boy Kento is alive?! And now he become Kamen rider Calibur, but he on neutral side?! NOOOOOOOOOOOOOOOOOOOOOOooooooooooooooooooooooo!!!! *Screaming in shock tone*

???: Big bro, keep it down!!!!

Making him startled and flinch, hearing the sound of his younger sister through the other room. Like a neighbour shouting the room.

Sam: Sorry, little sis! *Sigh & facing his computer* Onore that Reika bitch.... First she turns against Touma's friend and now she became Kamen rider.... Ugh! I wish Touma and others be friends again!

He turns facing seeing all the collections of Kamen riders and Animes. That right, Sam is the Otaku and big fan of Animes.

Sam: *Sigh* looks like, I had to play my favourite games on my phone.... Honkai Impact 3rd or.... Bang Dream.

And now Sam playing the game on his phone, wearing of the earphone on his ears. Choosing between the girls is Honkai Impact 3rd or Bang Dream. So he decided to play Honkai Impact 3rd.

Seeing Sam playing the game successfully playing the game against on the Enemy and finally defeated.

Sam: *Sigh* Kiana.... You are my truly Number 1 waifu, that I love you so much.... I really wanted to meets you as well... *Sigh in dreamily*

Until his fantasy were ruined, making Sam released the big sigh. And turning at someone he knows his grandpa, Rick Sanchez.

Sam: *Sigh* What do you want, Grandpa?

Rick drinking alcohol on his Flask.

Rick: Listen up, *burp* Sam... I'm came here to come by and I'm sick and tired of your *burp* ball [Beep], that you screaming like the 9 years old....

Sam: Yeah, yeah, yeah.... What you doing here? You didn't come by and visit us how we're doing since mom and dad die... *looking at the ceiling play with his ball*

Rick: *Sigh* Betty.... I know she was my daughter you know, your own mother. She even inherited of my geniuses become the dimensional traveller. *Sad tone*

He forms the sad looks expression, to seeing the old photo of young Sam with baby Harley with their own parents are smiling.

As Sam forms the sad looks expression on his face.

Sam: I know.... But anyway what you doing here? You never come by and visit us in Japan.

Rick: Technically I need you to come with me. There something I wanted to show you...

Sam: Okay, why? *Curious tone*

Rick: Well....

*Ding Dong*

Making them snaps out, as Sam rushes down before opens the door. Revealing is Fumina Hoshino. She is the classmate and close friend of Sam.

Sam: Fumina, what you doing here? *Surprised tone*

Fumina: Hey, I came by to see you and we're got plan for the studying. *Smiling*

Sam: Oh.... Oh.... Ohhhhhhh!!! *realization tone* I kinda forgot about that! Come... Come in for tha.... *cut*

Suddenly in the blink of eyes, there is the quick blurry thing charging toward on Fumina. Revealing is the tranquilizer dart hit on Fumina's chest.

As she opens wide, causing her to be knock out in cold. As Sam opens wide with the reaction looks on his face. Before turning face at his grandpa with the tranquilizer dart.

Rick: Ugh! What kind of gun is this?

Y/N: Gahhh!!! Grandpa, what the hell did you do?!?! *irritated tone*

Rick: Relax, she isn't dead. I just knock her out in cold for that.

Y/N: What we're going to do with her?!?! *Point at Fumina*

Rick:...... Sh*t. I do not think that true.... Come on, we're bring her to us. And calls your sister with us.

Y/N: Okay, what is going on here?

Timeskip brought you by meme!

And now seeing of Y/N carrying Fumina in bridal style, first one exited through out of the portal alongside his grandfather and younger sister Harley Stein.

Sam: Okay, this is the terrible idea. Bringing my classmate with me you terrible old man. *glare at Rick*

Rick: Hey, that wasn't my fault. In my defense.... I thought that was the Galactic Federation. *drinking his faisk* So not my fault.

Sam: Right.... So where I'm going to place her?

Rick: Put it on my bed, and she will be fine.... *instructed him*

As Sam placing Fumina on the bed to be resting, as Sam turns facing his grandpa.

Sam: Okay, grandpa where are we?

Rick: Okay, at first don't hate me... Do you remember Summer and Morty, your cousin?

Sam: Yes, wh... *realization tone* Oh no...

Seeing the door opens, and making them turns toward facing at someone. Revealing is Sam and Harley's cousin Summer.

Summer: Oh my go, oh my god! Sammy! Harley! *Smiles in excited tone*

Harley: Summer! *Smiles, rushes to hug her*

Sam: *Sigh* Hey, Cuz.... good to see you... *annoyed tone*

Summer: Oh don't be just a party poopers. Come on, mums and dad will be exciting to see you.... *Smiles and texting her phone*

Sam: Yeah... Ri... Wait, mums? *Dumbfounded tone*

Rick: Yeah, that going be the long story and awkward, just come to see it by yourself... *drinking beer*

And now Sam and Harley enter in the living room, as their grandfather follows them, revealing there is two Beth in the living room!!!

Beth

Space Beth

Sam: What the heck.... *Shock tone*

Beth: Oh! Sam, it is good to see you again! *Smiles*

Space Beth: Did Beth bring you here so he can make us to be as the Lab rats again? *cold and bitter tone*

Harley: There.... Two aunties.... *Shock tone*

Jerry: Hey, there Sam and Harley it been a long time, since I see you. Give your uncle a hug. *Smiles*

Sam: Nope, you're too weak and annoying.... That why my dad and mom hate you and doesn't like you that much.... *Roll his eyes*

Harley: No thank you, mommy and daddy says you're a loser man. *moving away*

Jerry:.... That is true... *voice breaking and sad tone*

And now Sam spotted seeing of his most annoying wimpy ass little cousin is Morty Smith. As they have the conversation.

Sam: Morty....

Morty: Sam....

Sam: It been a long time...

Morty: Yeah...

Sam: How you doing?

Morty: Good....

Sam: Man, last time I remember you still a wimpy and still complaining alot. And still a virgin loser. *Smirk and teasing tone*

Morty: What?! O-Oh, O-Oh, Oh yeah! The show you watch on Anime is suck! Anime is the ball of Sh*t! *anger tone and irritated tone*

Sam: What did you says?!?! *Anger tone and on rage*

As Sam throw the kick on Morty's nut!!!!

As Morty laying down on the floor, while he letting out of the whining sound and cover his nut.

Sam: Never insult anime.... *Demonic tone*

Morty: O-Oh okay..... Ow.....*whining and wince in pain*

Timeskip brought you by a chibi Sam invent Build Gundam for Build and Winning Gundam For Fumina

And now seeing of the Smith Family with Steins siblings are currently eating of their dinner.

Beth: So, Sam.... How you do today? How was life? *Smiles*

Sam: Hmmm? Oh yeah, yeah, yeah, yeah well... It's doing good and alright for that. I has joins the Science club for that.

Harley: Big bro already got the 15 medals of his geniuses!!! *Puff in proudly*

Rick: Yeah! That my grandson! *Smiles and proudly*

Space Beth: Oh.... Yeah, you only care and proud of Betty's intelligence and love more then us.... *bitter tone and glare at Rick*

Beth: Yeah.... That is true... *bitter tone and glare at Rick*

Rick: Looks, I get it.... I get it... I know I hasn't spend time with you and lied to you and send one of you in Space. I know this isn't Betty.... *cut*

Beth: Of course, this is always about Betty! It me! Our lives!!! *anger tone & stood up from her sit glare at Rick*

As there is the intimidating aura surrounding on the atmosphere between of the father and his daughter plus the clones.

As Sam broke the awkward silence.

Sam: Okay.... How about, we're just leave out....

As they're nodded their head and started to be leaving.

Timeskip

After the arguments of Rick and his daughter with the clone too, about Beth always jealous her sister Betty is more superior then her.

And now seeing of Sam with Hayley are waiting for Rick arriving before, he enter in the garage.

Rick: Whooo! Sorry about that. You see.... Me and your aunties have heated arguments for long time....

Sam: Okay.... So why you brought us here?

Rick: This....

He remove the sheet from the large device, revealing it is the machine.

Sam: What is that?

Rick: Th-This is the teleportation device! *burp* You see this is the prototype, but it's similar to my portal gun. It can always to teleported including the place to the another dimension. That why I needed your helps because you have the mind of the genius!

Sam: So.... You needed my help so I can help you build of the machine?.... Okay, let do this! *Smiles*

Rick: Okay... By the way... Here your belt toy....

As Rick tosses the item toward on Sam, as he manages to catch it in his hand. Revealing his Build Driver!

Sam: My Build driver! Wait... It feel... Little bit heavy. *felt the bit heavy*

Rick: Nah, don't worry about it. I manage use portal gun to bring Build Driver into another world after I read many Isekai Kamen Rider Fanfiction in your laptop. I arrive an fantasy world and then I check Build Driver turn into real. 

Sam: Really? So.... I can henshin?

Rick: Maybe.... Let go to work....

And now seeing of Rick and Sam are building the device, spending time as grandfather and grandson. While Harley is reading her book.

And now they finally succeeded building the device.

Rick: Damn! We're finally finished! *Smiles*

Sam: Yeah! *Smiles*

Rick: Now.... Sam would you do the honors? *Smiles at Sam*

Sam: I like too.... *Smiles*

And now seeing of Sam started to be typing on his computer, as it glowing in green. Suddenly everything on the ground started to shaking and rumbling. 

Making Sam to be opens wide, before looks down, see the sign says "Warning" in multiple on the screens.

As the top bulb glowing in brighter with the green, as Rick hold on something before Sam glance at Rick.

Sam: Grandpa something is wrong! *panick tone*

Rick: No sh*t, Sam!!! I don't know what the hell is going on!!! Find something to shut it down!!!!

Rick: I'm trying! It not working! *try something eyes typing but not working*

Until then Morty and Summer arriving to the garage, with the cautious looks on her face.

Summer: Grandpa Rick, what is going on?! *panic tone*

Morty: Oh geez, Rick! That isn't looks good as well... *panic tone*

Sam: Oh no.... It going to be explode! Hang on!

As it started going in brighter before it released the shockwave hit on everyone. Making them fly and pushed.

Until then they have been vanished alongside the part of the Garage has been gone. Seeing the door is open. Revealing is Jerry.

Jerry: Wh-What the heck is going o.... Gahhhhhhhhhhhhhhh!!! What the hell happened to my garage?!?! *Shock tone*

Seeing of Sam and his family started to be screaming around in their garage flying in the void of the multiverse. Sam turns notices.

Seeing of the savior fight Darksied, the golden warrior fight the triangle demon, the ancient beetle fight against the kid wearing red cape and red mask with dark aura, and seeing of the amazing spider hero fight against plague doctor

And then they landed next to the abandoned cafe not of nowhere, before releasing the big dust.

While the other family are groaning in roughly, feeling their body and bones broken for the bits.

Sam: Well.... That gonna hurt.... Grandpa... Where are we?

Rick: Alright, alright, alright. Let me check... *get up and check the machine* Hmmm.... It says Dimension A-Prime 1

Sam: Dimension A-Prime 1? I never heard of this. Did you know about it? *looks at his grandpa*

Rick: Nope! I had no idea for that.... *drinking his flask*

Morty: Oh geez.... What we're gonna do, Rick? Do you had your portal gun? *looks at Rick*

Rick: Hmmm.... In the better in I do... *take out his item and looks at it*.... F**k!

Summer: Language! *cover Harley's eyes*

Sam: Wait, what happened? *looks at his grandfather*

Rick: The portal gun has been damaged since we're arrive here.... It can work travel to the another planets and dimension but it damages and we're can't go home!!! *serious tone*

Making them to be let out of the opens wide.

Summer: Wa-Wait! Do you means we're stuck here?! Nooooooooooooooooo!!! How am I supposed to text my friends here!!! *looks at her phone*

Sam: *Sweatsdrop* Okay.... But first we need to take care....

???: Kyahhhhhhhhhhhhhhhhhhhhhhhhhhhhhh!!!!

Making them flinch and facing them toward, hearing of the female screaming sound. Making them to be rushes seeing Fumina has woken up and seeing the creatures is....

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

Grimms!!!

Sam: Holy crap! Is that Grimms! And it real?! *felt excited and fanboy*

Rick: Great! Take this weapon! And use it to fight these black bone monster! *throw weapon at Sam*

Sam grab the weapon and it was cyber rifle gun as Beowolf jump at Sam but he dodge it and Sam shoot at Beowolf as it was scream in pain.

Sam keep shoot at Grimm as they were die and turn into dust while Sam keep shoot at Grimm and Grimm were kill by Rick hold pistol.

As they're turns seeing of Rick, killing the monsters while currently holding of his pistol and his other hand holding the flask.

Rick: You're welcome by the way... *drinking alcohol*

Sam: Fumina you're awake! *notices her*

Summer & Morty: Who is she?!

Fumina: Sam..... What the heck is going on?!?! *glaring at him*

Sam: Ummmmmmmmm......

Timeskip brought you by meme!!!

And now seeing of Sam in the city of the Neo, as he have the astonished and fanboy looks on his face. Seeing the different anime cultures.

Sam: Holy crap.... It looks like, I'm in the Paradise of this worlds. *notices*

Seeing the guy has the quirks

Sam: Quirks! It the superpowers ability from my favourite Manga, My Hero Academia!!!

Seeing the man has Sacred Gear

Sam: Sacred Gears! it the powerful relic ability from the erotic light novel and anime known as High School Dxd!

Seeing the guy with magic.

Sam: The Magic! It is the supernatural abilities from Fairy Tails and irregular at Magic High School! I could live here foreverrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr!!! THIS IS THE BEST DAYS OF MY LIFE!!!!!!!!!!!!!!!!!!!!!!!! *fanboy tone*

Fumina: Sam.... This is no time to play. We need to do something. *Serious tone*

Sam: You're right. Sorry. *Apologize tone* It just.... It like the dream come true.... *Smiles in fanboy*

As Sam accidentally bumps on the girl, making him turns toward and opens wide. Revealing the girl with guitar case is Kasumi Toyama!!!

Kasumi: Sorry! I got to go! *apologize tone and rushes*

Sam's mind: Holy crap! Is that..... KASUMI TOYAMA FROM BANG DREAM, THE MAIN LEAD PROTAGONIST OF THE BANDORI. SHE IS THE LEADER AND VOCALIST OF POPPIN 'PARTY! SHE IS MY ONE OF FAVOURITE WAIFU WITH YUKINA AND I LOVE HER SONG SO MUCH!!!! *fanboy*

Seeing of Fumina scolded on Sam, but unaware being watch by the person on top of the building.

???: The time has come huh? It time for the attack....

While two friends are walking, suddenly they're heard the explosion from the sound of boom. Making them turns toward.

Revealing is Guardians! They're begins to terrorizing and attacking of the innocent people.

Sam: What the hell?! Guardians?! *Shock tone*

Fumina: No way... Why?! *Shock tone*

Guardian take out their gun and shoot at many people as they were got hit while people run away and Guardian take out the guns to shoot at women & child.

Making Sam rush as he punch at Guardian but he was block it by his hand before punch at his guts and make Sam spilled silvia. The women carry the child and run away.

Fumina: Sam! *worried tone*

Sam struggled to get up, until he spotted the Build Driver in his back. As he opens wide and remember of his grandpa told him once.

He crawling toward, before getting of his own driver. He slowly getting up returns back to the ground.

Sam: If Grandpa said it true.... Maybe I become a hero! *determine tone*

He slammed the driver on his waist, as the yellow stripped wraps around on his waist to fit in.

Sam: Holy crap! It work like Kamen rider! *fanboy bit and turn smirk* Saa.... Shall we're begins the experiment? *Smirk*

He shook the bottle, as the equation appears, making the Guardians to be confuse before he twist it.

Rabbit! Tank! Best Match!

He crank the lever.

Are you ready?!

Sam: Henshin!

(Techno rock music) Hagane no Moonsault! RabbitTank! Yeahhh!

Sam transformed as Kamen rider Build!

Build: Holy crap! Holy crap! I just transformed into Kamen riders! *fanboy and excited tone*

Fumina: No way! *surprised tone*

???: Ohhhhhhh!!!! He transformed as Kamen rider Build! This could be excited! *grin & watching him*

The Guardian charged at Build as they shot at Build but he dodge it by use superspeed and he jump before he kick at Guardian.

The Guardian were keep shoot at Build but he use tank as he create defense and protect himself from bullet. 

Build charged his fist as he keep punch at Guardian rapidly time as they were scream in pain before Build release powerful punch at Guardian as they were explode.

Build: Let finish this!

Ready, go?! Vortech Finish!

Build jump and create math graphic as it stuck on Guardian and it can't escape before Build slide down on math graphic and he slide kick at Guardian as it was explode.

Fumina: Sam, you did it!

Build: Yeah! This is so much, cool!

???: Freeze!

Making them startled and flinch, and making them turns toward seeing of the Atlas lead by General Ironwood!

Build's mind: Ugh! Not him! Why here?! Everyone not him, but he has gone too far for that!!! *Anger and hatred tone*

Ironwood: Vigilante stand down! Put your weapons down! *order tone*

Build: Hey! Can't you see that! I just save your bloody ass, and I'm the Kamen rider!

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

Ironwood: What the hell is Kamen rider?

Build:..... You're f**king kidding me, right? *Felt anger and glaring at Ironwood* Screw this! Fumina grab on me? *instruct her*

As Fumina grab and held tightly on Build leaning on his chest. She blushed a little before she could ask him.

Suddenly Build fired the portal gun, causing them to be drop down, as Fumina releasing of Screaming while Build flipped the bird at Irondick.

As the portal vanished, while the Atlas staring in dumbfounded and shock looks expressions. As Irondick snaps out.

Irondick: Don't just stand there! After him! *order tone*

Atlas: Yes, sir!

Ironwood's mind: I will found out, who you are masked vigilante....

At the person he smiling in amusement.

???: This is the amazing! Totally amazing, now let the games, begins! *grins*

At Sam

And now seeing of the Smith + Stein siblings included Fumina are currently sitting down on the couch.

Sam narrator: And so yeah, we're don't have to find the way to go home.... But grandpa will tell us he will find the way to go back home. But he decided to opens the cafe to cover for us. You know.... Grandpa may be the arrogant and asshole prick but.... He do have the heart and love us. We're family you know.

Showing Sam & his family decide to take picture in front of the garage as Rick take camera and he leave it and stand nearby with his family before camera take picture.

At C-137

Seeing the New Galactic Federation is in ruined and under attack by the large ships. Seeing the alien species known as Gromfloites bleeding. Trying to crawl way out. But get grabbed and pulled by the person.

???: Now then.... Where is Rick Sanchez? *cold tone*

End of Chapter 1 

Next Chapter: Join World Hero Academy And Meet Ryusei Kudo

So what do you think? I decide to make first chapter of Build X Animeverse with Sam as grandson of Rick Sanchez. This time they will face enemy from alternative future and next chapter is Sam join World Hero Academy and meet Ryusei Kudo aka idiot meathead. Thank you for the idea, Doct. See you next time!