It's been a day since Nick stopped the Hundred from invading his World. Right now, Nick's decided to test out his new Dimension traveling abilities.
Nick: "Okay. Seeing as I now have Tsukasa's powers, I should be able to use Aurora Curtains to travel between Worlds. (sighs) Okay, here we go..."
Nick raises his right hand, and focuses. Causing an Aurora Curtain to open in front of him, and transport him to another World.
Nick: "It worked. Awesome. But...where am I?"
Nick looks around, only to see a large city in front of him. Nick then rummages his pockets, finding a Duel Monsters Deck and a magenta Duel Disk.
Nick: "A Duel Monsters Deck? And a Duel Disk? I must be in a World of Yu-Gi-Oh. Specifically, one of Arc-V, judging from the model of the Duel Disk. I wonder what my cards are. (looks through the Deck) "D/D" cards, huh? Kinda fitting, if you ask me."
For those who don't know; "D/D", pronounced "Double D", means "Different Dimension".
Nick then activates his Duel Disk, finding his ID, which says he's a transfer student at Paradise Prep School. And he's 14 years old.
Nick: "So, I'm in Paradise City. And, 14 years old? What the heck? Does my new "role" in this World require me to be younger? Whatever. Guess I better head to my new school."
Nick then travels through Paradise City, guided by his Duel Disk's map, eventually arriving at Paradise Prep School. Soon, Nick registers as a new student, and reaches his new home room.
Teacher: "Alright, class. Today, we have a new student joining us. Come on in."
Hearing this, Nick enters the classroom, and stands in front of his new classmates.
Nick: "It's nice to meet you all. I'm Nick Brown."
Nick notices that two of his classmates are none other then Yuya Sakaki and Zuzu Boyle. Nick then spends the whole day attending classes. To which, he was...very bored, being in a classroom again. Eventually, school was over. Nick decided to head to the You Show Duel School, where he runs into Yuya and Zuzu.
Yuya: "Hey, you're the new kid at school. What are you doing here?"
Nick: "Well, to be blunt...I'm hoping to Duel you, Yuya."
Zuzu: "Wait, seriously? You came all the way to You Show just to Duel against Yuya?"
Nick: "Uh, yeah. Duh."
Yuya: "Well, you're on, new guy."
Nick, Yuya and Zuzu then enter the You Show Duel School, where Nick meets Yuya's father; Yusho Sakaki, Zuzu's father; Skip Boyle, as well as Allie, Frederick and Tate, as well as Sore Perse, Shay Obsidian and Alexis Rhodes, with the latter three having be visiting. Nick and Yuya then enter the arena.
Yuya: "Alright, new guy. Hope you're ready to Duel."
Nick: "Well, guess we're about to find out. By the way, I've never been in an Action Duel before. Though, I do know how they work. Like with the Action Cards."
Yuya: "Oh really? Well then, guess this'll be your first real Action Duel."
Yuto's spirit then appears next to Yuya.
Yuto: "Be on your guard, Yuya. There's something odd about this person."
Yuya: "Really? If you say so, Yuto."
Skip then activates the Action Field, being "Acrobatic Circus". During the Duel, Yuya and the others were all shocked by Nick's usage of "D/D" cards. Eventually, Nick manages to beat Yuya.
Sorry, I didn't know how to write a Duel for this, so I just skipped it.
Nick, Yuya and everyone else chill in the rest room, where Nick reveals that he from another Dimension, one outside the Four Dimensions of Pendulum, Xyz, Synchro and Fusion, where Duel Monsters is a regular card game, and Duel Disks are plastic toys. Nick also reveals that he knows that Yuya is the reincarnation of Z-ARC and Zuzu is the reincarnation of Ray Akiba. Nick can also see the spirits of Yuto, Yugo and Yuri inside Yuya, and the spirits of Celina, Lulu Obsidian and Rin within Zuzu. Nick suddenly asks Yusho and Skip if it's alright if he crashed at You Show, due to not really having a lace to stay. Instead, however, Nick was invited to stay over at the Sakaki House. The next day, Nick, Yuya and Zuzu walk to school together. Though, Yuya was strangely kinda blushing while near Zuzu, due to a late-night conversation he had with Nick last night. Suddenly, an Aurora Curtain opens on the school grounds, with Kasshines emerging from it, causing everyone to panic.
Yuya: "What the heck are those things?"
Nick: "Kasshines."
Zuzu: ""Ka-Shines"?"
Nick then notices an Another Rider, being Another Ryuki, emerge from the Aurora Curtain.
Nick: "And Another Ryuki. I'll handle this. You guys get to safety."
Yuya and Zuzu simply stand there, as Nick walks towards the Kasshines and Another Ryuki, as 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 transformed into Kamen Rider Decade, shocking Yuya and Zuzu. Decade then pulls out the Slash Card, sliding it 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 then looks towards Another Ryuki.
KR Decade: "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.
KR Decade: "Rider Change!"
NeoDecadriver: KamenRide: Ryuki! (V Buckle transformation sound)
Decade had now transformed into Kamen Rider Ryuki.
KR D-Ryuki: (clenches his fist) "I'm not going to die. Because once you take a person's life, there's no turning back!"
D-Ryuki then charges at Another Ryuki, and starts slashing it with the Ride Booker, gaining the advantage against the Another Rider. Soon, both D-Ryuki and Another Ryuki burst through a window, entering a Mirror World resembling Paradise City.
KR D-Ryuki: "Honestly, I'm really surprised that the World of Yu-Gi-Oh has a Mirror World. Pretty much every Dimension in the Multiverse has one."
D-Ryuki the proceeds to fight Another Ryuki, before pulling out a new Rider Card.
NeoDecadriver: AttackRide: Sword Vent!
NeoDecadriver: AttackRide: Slash!
Suddenly, a large, red Western Dragon, known as Dragreder, appears, as it's tail becomes a sword, which D-Ryuki wields in the battle against the Another Rider.
KR D-Ryuki: "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: Ry-Ry-Ry-Ryuki!
D-Ryuki then takes on a readying stance, as Dragreder flies around him. D-Ryuki then jumps into the air, flying towards Another Ryuki, as Dragreder sets D-Ryuki on fire.
NeoDecadriver: Final Vent!
D-Ryuki delivers a Rider Kick across Another Ryuki. Once D-Ryuki lands, no longer on fire, Another Ryuki explodes, leave nothing left of the monster. D-Ryuki then exits the Mirror World, before turning back into Decade, and then back into Nick. Yuya and Zuzu.
Yuya: "Dude, what the heck just happened?"
Nick: "It's a long story, dude. Anyways, I better get going."
Zuzu: "Wait, you're leaving?"
Nick: "Yeah, that sums it up. But, I'm definitely coming back to visit."
Nick then summons an Aurora Curtain, and walks through it. Leaving the World of Yu-Gi-Oh, and into another Dimension.