In the year 2014...
It starts at the scene where Go Shijima, Kamen Ride Mach and Chase, Kamen Rider Chaser are fighting against Tenjuro Banno, Kamen Rider Gold Drive.
Unfortunately for Go and Chase, Tenjuro have beaten them, forcing the two to de-henshin.
Tenjuro was about to be finished off, but suddenly, Y/n appeared in his Zi-O II form, caught Tenjuro's attention by hearing his footsteps.
Tenjuro: Who are you?
Y/n didn't say anything, except engaged Tenjuro with his dual wielding weapons.
Y/n managed to get the advantage on damaging Tenjuro.
Tenjuro stole Y/n's weapons and engaged him again. However, Y/n is more skilled than Tenjuro even with his weapons and beated him down to the ground.
Tenjuro: What?
Zi-O II ...Time to end this.
Rider Finish Time! Twice Time Break!
Y/n then finished Tenjuro off with a rider kick.
After the explosion, only Tenjuro's belt remains.
Y/n then grabbed out a blank ridewatch and absorbed what's left of Gold Drive's data, causing Tenjuro to cease to exist.
Gold Drive: What the...? N-No, what's-? Agghhhhhhhhhhh!!!
Then, Gold Drive suddenly disappeared, leaving only his broken belt on the ground and Y/n getting the Gold Drive Ridewatch.
Y/n then immediately walked away.
Go, Chase, and Kiriko Shijima, who was also there, tried to figure out what happen, but they wasted no time and left the scene immediately for a reason.
Later...
Y/n is walking outside of the parking lot, trying to find an empty space.
Y/n: *sigh*17 down, and 1 one to go.
Y/n then picks up and looked at his last ridewatch.
Y/n: Koemi...
Y/n then had a flashback where Koemi has been kidnapped by Mitsuru.
Y/n: -Where are you?
Y/n then started to grabbed his last blank ridewatch and attempted to throw it, but he suddenly hears someone.
???: Wait.
The area around Y/n then appeared all black.
Then, the black part seems to televised away, leading back to a very familiar place Y/n was in, the cloaked man's psyche plane.
Y/n: This place...
???: It seems you have only one more rider's power that you must gain.
Y/n: Old man. What am I doing here again? What do you want?
???: I'm here to warn you that this world you are going is unlike any other you have faced. I brought you here to let you know that I will be the one to send you to that world.
Y/n: If that's the case, then get on with it.
???: You seemed anxious, Y/n. I something on your mind? Does it have to do with what happened to your friend.
Y/n: Shut up, old man. Koemi is not your concern.
???: But it is. Y/n, you declared and desired you want to be king. If some disturbance is throwing you off that path, you may be doomed to fail.
Y/n: Koemi is not a disturbance! Don't treat like some rock in front of the road!
???: Then it's not about her, it's about Kamen Rider Savior. Yes, I foresaw the events and he beaten you again.
Y/n: ...He's just too strong. If I'm going to be king, then I have to be stronger than him and have the strength to protect other people. But I... I couldn't even save Koemi.
???: So it's power you want. Then I may be able to answer your calling.
Y/n: Huh?
The cloaked man held out his hand and Y/n's Zi-O Ridewatch and Zi-O II Ridewatch were being pulled to the cloaked man.
Y/n: Hey, what are you doing?
The cloaked man grabbed the ridewatches and held them out.
The Ridewatches and the cloaked man formed a triangle and a ridewatch suddenly appeared.
The cloaked man handed back Y/n his two ridewatches, including the new ridewatch.
note: imagine Y/n's Trinity face being on, the white being black, and pink being red.
Y/n: A new ridewatch.
???: That ridewatch has the power of your personal, Zi-O II's, and a little bit of mine.
Y/n: Yours? Wait, old man, are you a Kamen Rider?
???: ...Yes, but not anymore. Y/n, if you are ever in dire need of power, use that watch.
Y/n then stared at his new ridewatch he has.
???: Now then, it's time for me to send you to the final world.
The cloaked man raised his hand and hit Y/n with a beam of light.
Y/n was seen covering his eyes because of that bright light and the screen faded to white.
Timeskip...
Y/n suddenly woke up on a couch and immediately sit up.
He looked around to be not a normal house, but something else.
Y/n: What the hell is this place.
Suddenly, an old man appeared with a tray of tea and a wet towel.
???: Oh, good! Seems you're finally awake.
Y/n: Who are you?
Eijiro: I'm Eijiro Hikari, nice to meet you, um...
Y/n: Hmph, Y/n L/n. Nice to meet you too, I guess. What is this place? How did I get here?
Eijiro: That's what I like to know. I saw a flash out of my front door and I found you unconscious.
Y/n: I see.
Eijiro: Do you remember how you got here? Do you remember anything?
Y/n: I'm don't have amnesia, old man. I do remember, but I don't want to bother explaining.
Eijiro: Geez, you didn't have to call me "old man" you know?
Y/n: Whatever. Anyway, what is this place?
Eijiro: Oh, this place you're in is the Hikari Studio. You may not realize but this is a photography studio, and I happen to be the one running this place.
Y/n: Is that so?
Y/n then gets up and walks around.
Then, he spots a screen of a photo of a bunch of riders and monsters attacking a single rider.
Y/n: Nice photo you have.
Eijiro: Oh that... That's not really mine. This may be hard to explain to you. But they're-
Y/n: Riders. Kamen Riders.
Eijiro: How did you...?
Y/n then gets out his personal ridewatch and showed it to Eijiro.
Eijiro: You're-
Y/n: I also happen to be one.
Eijiro: Wow... Such a surprise.
Y/n: Anyway, what is this photo here?
Eijiro: Uh, well this photo here actually shows another world.
Y/n: Another world?
Eijiro: Oh right. It may be hard to explain-
Y/n: Not really, I happen to be traveling to other worlds as well, even other times.
Eijiro: Wow, to think there's someone else who can travel instead of us.
Y/n: Hm?
Eijiro: Oh, sorry I was elsewhere. Where was I? Oh yes, the world which you are seeing here in this photo is the World of the Rider War.
Y/n: A war? Like, between riders?
Eijiro: Well...
Y/n then sees and slowly walks up to see one rider in the picture who looks like is being targeted.
Y/n: Mr. Hikari. Who is this rider right here?
Eijiro: Where?
Y/n: *points his finger*This one, who looks like he's glowing. Like he's the one being targeted.
Eijiro: ...That's Tsukasa, or Kamen Rider Decade.
Y/n: Decade... You know him?
Eijiro: Yes, he's our comrade in our journey.
Y/n: Journey?
Eijiro: Long story short, me, my granddaughter, Tsukasa, and some other comrades are traveling through worlds. Trying to prevent them all from merging together.
Y/n: What happens if all those worlds merge together?
Eijiro: *sigh*Then they will all be destroyed. But thanks to Tsukasa, he's been finding a way to stop this disaster from happening.
Y/n: Then why is, uh... Tsukasa. Being targeted by the other riders when he's trying to save them.
Eijiro: Because someone Tsukasa met says that he's the Destroyer of Worlds. They believe Tsukasa's existence threatens to the worlds and he's destined to destroy them. But I don't believe it, Tsukasa would never do such a thing.
Y/n: How ironic... That a rider tried to save the worlds, but will end up being destroyed. Where is he now?
Eijiro: I don't know. He, my granddaughter, and the others haven't come back, so I'm a little worried.
Y/n: ...Well, since I'm here, might as well go find him.
Eijiro: Really? You would really do that?
Y/n: Why not. I may have come to this world for another purpose, but I always find the opportunity to help others. *thoughts*This is what Koemi would've wanted after all.
Eijiro: Thank you so much, Y/n.
Y/n then left the front door and got his bike out.
Eijiro: Y/n! Please make sure everyone comes back safely.
Y/n: No promises, but I'll do my best.
Y/n then rode his bike to find Tsukasa.
Meanwhile...
Tsukasa Kadoya, Kamen Rider Decade is about to face the 9 Heisei Riders.
Decade: Come. I'll destroy you all.
All the 9 riders charged at Tsukasa one by one.
It becomes a lengthy battle where Tsukasa battles all the 9 riders by himself and lasers were fired everywhere.
Daiki Kaito, Kamen Rider Diend, then charged at Tsukasa holding him on gunpoint.
Then there was a moment of freeze.
Diend: Tsukasa.
Decade: Kaito.
Diend then pulled the trigger of his Diend Driver.
Natsumi Hikari was shocked when she witnesses it.
Natumi: Decade!
However, everyone was surprised when Kaito missed his shot, and his driver got fired off his hand.
Everyone is wondering where it came from, that is until they saw the Taka watchroid flying and shooting out fire.
Then, Y/n appeared on his bike and landed on the ground and began charging where the riders are.
Kiva A.R.: Who is that?
Y/n then got in front of Tsukasa and hit the 9 riders, except Tsukasa and Diend with the backside of his bike and sent them all back.
Y/n then got out of bike and its ridewatch and the Taka watchroid were back in his hands.
Y/n: *faces Tsukasa*Are you Tsukasa?
Decade: ...I am. And you are?
Y/n: Y/n L/n. Kamen Rider Zi-O.
To be continued...