An alarm clock goes off, showing the time as 9:00 am, before being turned off by a teenage boy with reddish-brown hair and green eyes, with his ears protruding from his head, and a scar running horizontally under his left eye and above his left cheek. His name, is Nick Brown.
Nick: (groans) "Stupid alarm clock." (sighs and gets out of bed) "Whatever."
Nick is then seen in the bathroom looking at himself in the mirror.
Nick: "Well Nick, it's time for yet another boring normal day, in this boring normal world. I wish I was in a world where things interesting happen. Especially sense I've FINALY graduated from high school a few months ago and my nineteenth birthday has passed yesterday, and Summer Vacation is almost over, for Grey, Issy, and Gaby at least."
Nick then leaves his family's house, as he decided not to move out and live with his family while using his paychecks to help pay with bills, and goes for a walk through town. We now see Nick walking down a hiking path in the town's local forest. Nick doesn't know what to do, as he has just graduated from high school after having to take an extra year due to the Covid-19 Pandemic. Nick's application for a college that's in a town two hours away from his was declined as there was no open spots, so Nick was now waiting for any opens in town so he can get a job, as he applied for a job at the local Dollar Store, and gas station, he's just waiting for them to call him for an interview. Which wasn't easy, seeing as Nick has autism, making job hunting difficult for him. Nick never had a good high school life, as all of his male "classmate" always mocked him for being autistic and having an overactive imagination, and other things that make Nick who he is, this leading to him becoming a loner at school with an extremely fragile trust in other guys, especially when his male "friends" from middle school all started to hang out with his bullies and one even calling him a "piece of trash", leaving him to only be able to trust his female classmates. Nick is also the only guy his age at his school who graduated, as all the other male "students" his age were literally stupid, always disrupting and having their phones out in class, making inappropriate comments, breaking all the school rules, drawing inappropriate things on the stalls in the boys' bathrooms, failing every class their in, skipping classes, not to mention the massive after school, weekend, and summer detention records, and failing grades to the point their all still in ninth grade while Nick graduated with passing grades. Nick had been living an ordinary life, and he wasn't comfortable with it. It wasn't like he had a girlfriend or anything, seeing as girls never showed any romantic interest in him, and ever since his sorry excuse for a "biological father" abandoned his family years ago, Nick mentally blocked himself from falling in love ever since he was ten years old, this is out of fear that he would end up the same as his "father", some one who would neglect his family and then disappear leaving zero good memories with his children, leading them to hate him forever. Plus, Nick's mother didn't have a good "father" of her own, as hers was an abusive alcoholic. Nick has excepted this and never looked for a love life, deciding to just stay single forever, not like he cares for something he sees as pointless and worthless. Nick is now seen exiting the forest and into an open space next to a river dam overlooking the bridge on main street that leads out of town. As he is walking to the field, he spots a mysterious, yet familiar, magenta belt on the ground, with book next to it.
Nick: (picks up the belt and book) "Are these a toy NeoDecadriver and a Ride Booker? What are these doing here? I didn't think anyone else in town but ME even KNEW about Kamen Riders. But, why would someone just leave these on the ground? Eh, I guess if someone left these here, then I could just keep them."
Nick then continues walking onto a pathway, entering the main street. Suddenly, an explosion appears in the road.
Nick: "What the heck?! Was that an explosion?!"
Nick runs towards the scene, as he sees police officers shooting was appeared to be robots.
Nick: "Wait, are those Kasshines? But those don't exist, in THIS world anyways. What's going on?"
Police Chief: "Shoot them down!"
Police Officer 1: "We're trying, but our bullets aren't doing ANYTHING on those things!"
Suddenly, a portal opened behind the Kasshines, as a strange red and blue monster walked out of it. Nick was shocked, as he recognized the monster.
Nick: "Is that Another Build?! What's an Another Rider doing here?! And, did just walk out of an Aurora Curtain?! I don't that was Hollywood Magic. This is real?!"
Police Officer 2: "What the heck it that thing?! Take it out!"
The police keep shooting Another Build, but the bullets just pounce of it. The Another Rider then starts beating up the Cops and threw a car at the police.
Nick: "The Cops don't stand a chance against Another Build, sense it has the power of Kamen Rider Build's RabbitTank form. Not to mention, only the original Rider, or a Rider with the power to change into the right Rider can destroy an Another Rider. So, with Kamen Rider Build, or a Rider who can access Build-based form, there's no stopping that thing."
Just then, the toy NeoDecadriver started glowing, and Nick got sucked into an Aurora Curtain, dragging him into what looked like the town, but nobody was there.
Nick: "What the heck?! Hello?! What's going on now?!"
???: "You don't have to worry, kid."
Nick turns around and sees a familiar person.
Nick (shocked) "Y-You're Tsukasa Kadoya! Kamen Rider Decade! But, didn't you DIE after your fight against Ohma Zi-O?"
Tsukasa: "You're correct about that, kid. I AM dead. This is subdimension in between the living, and the dead. I see you found my Driver and Book."
Nick: "Wait, these are the REAL NeoDecadriver and Rider Booker? I thought they were toys. Wait, you can stop them, you can defeat that Another Build."
Tsukasa: (shakes his head) "I can't do that. Like I said, I'm dead. I brought you here to give you a choice."
Nick: "A choice?"
Tsukasa: "You could put my Driver on, and use my powers to defeat the Another Rider, and the forces invading your world."
Nick: "Who are invading my world?"
Tsukasa: "The Hundred."
Nick: "The Hundred?! Their using Another Riders now?! And, what do you mean I defeat them with your powers?"
Tsukasa: "Yeah. Now, use my Driver, and fight the evil that's invading your world. Or, you could have someone else do the job."
Nick thought about his choices. He either uses Tsukasa's power, become a Kamen Rider, and save his home. Or, let someone else do it.
Nick: "I won't become a "Destroyer of Worlds". I'll become a "Defender" instead."
Tsukasa: (smiles) "Well then, what are you waiting for….Kamen Rider Decade."
Nick puts on the Driver around his waist. He then opens the NeoDecadriver, and pulls out the Kamen Rider Decade Rider Card from the Ride Booker.
Nick: "Kamen Rider!"
He then slides the card into the Driver, and closes it.
NeoDecadriver: KamenRide: Decade!
Nick is then surrounded by transparent holograms that circle around him, before covering his body, and become a grey suit. Cards then fly out of his belt and form a barcode on his helmet, as his suit changes from grey to magenta, completing his transformation into Kamen Rider Decade. Decade then walks through an Aurora Curtain, and back into his world.
Back in Nick's world….
The police are still struggling against the unknown invaders, when a magenta masked figure suddenly appears.
???: "Stand down, officers. I'll handle it from here."
Police Chief: "Who the heck are you?!"
Kamen Rider Decade: "I'm just a passing through Kamen Rider. Remember that. And you and your men should focus on getting people to safety. Normal weapons don't effect these guys, especially Another Build. But I can take them down."
Not having much other choice, the police chief orders his men to fall back, as Decade switches his Ride Booker into a sword, and places a new card into the NeoDecadriver.
NeoDecadriver: AttackRide: Slash!
Decade's sword then gets covered by energy, as he slashes it at the Kasshines, destroying them with ease.
Decade: "That takes care of the Kasshines. Now, for the "Wannabe Build". The only way to destroy an Another Rider, is with the powers of the respective Kamen Rider."
Decade pulls out a KamenRide Card and slides it into the NeoDecadriver.
NeoDecadriver: KamenRide: Build! Moonsault of Steel! RabbitTank! Yay!
Decade had now transformed into Kamen Rider Build, RabbitTank form.
D-Build: (Does Kamen Rider Build's pose) "The law of victory has now been set! Now, let's begin the experiment!"
D-Build then charges at Another Build, and starts punching it. Thanks to now being Kamen Rider Build, he has the advantage against his Another Rider counterpart.
D-Build: "I think it's about time I finish this fight."
D-Build then pulls out one last card and slides it into the NeoDecadriver.
NeoDecadriver: Final AttackRide: Bu-Bu-Bu-Build!
D-Build: (raises his index finger up) "Just a moment, please."
D-Build then runs away from Another Build, before diving underground, as a white chart flies up to the surface with the dotted line securing Another Build. D-Build then leaps back up, into the air.
NeoDecadriver: Ready, go! Vortex Finish! Yay!
D-Build then starts riding down the chart's line and delivers a Rider Kick across Another Build. Once D-Build lands, Another Build explodes, leave nothing left of the monster. The police chief then walks over to D-Build, who turns back into Decade.
Police Chief: "I don't know WHO you are, but, thank you for helping us with those things."
Decade: "The robots were called Kasshines. The red and blue monster I just destroyed was Another Build."
Police Chief: ""Another"? You mean there are more of that thing?"
Decade: "No, I mean it's name was "Kamen Rider Another Build". It's a monster called an "Another Rider". They're monsters that are corrupted versions of Kamen Riders, and the only way to destroy them is if you can turn into the respective Kamen Rider, or can use a form based off that Rider. Another Build is based off Kamen Rider Build."
Police Chief: "Well, either way, thank you. What is your name, anyways."
Decade: "I already told you, I'm just a passing through Kamen Rider. Remember that. But, you can just me, Kamen Rider Decade."
Police Chief: ""Common Rider Decade"? You keep saying "common", but I've never seen anyone like you before."
Decade: "Not that kind of common. It's spelled K-A-M-E-N, it means "Mask" in Japanese."
Police Chief: "So, you're from Japan?"
Decade: "I'll just leave that to your imagination. For now, I'll be on my way."
Decade then summons an Aurora Curtain which envelops him, as he waves at the police chief. Disappearing without a trace.
Time Skip….
After returning home, Nick told his family what happened. At first, they didn't believe him, until he transformed as proof, that he is now, the NEW Kamen Rider Decade, and the Defender of Worlds.