It starts off where we left off in the Sengoku time. Y/n and Koemi encountered a mysterious young man by the name of Mitsuru, Kamen Rider Savior.

Mitsuru: -And in order to keep time in place, I must kill you.

Both Y/n and Koemi are shocked hear those words.

Y/n: Who do you think you are saying those words!?

Mitsuru: Further explanations are unnecessary. *puts Ziku Driver on*

Koemi: Wait! Tell us why you want to hurt Y/n. He didn't do anything wrong.

Mitsuru: That's where you're wrong, Zi-O will use the dark power he has gain to destroy the future, my future.

Y/n: Wait, what are you talking about?

Mitsuru: Unlike you two, I come from an era from the future, in 2068. However, there has been a disturbance in the timeline, and I found out the cause was Zi-O. In time, Zi-O will become someone who's pure evil and destroy the world.

Koemi: You're wrong! Y/n would never do anything like that!

Y/n: Koemi...

Mitsuru: I do want to trust in you words, however in order to the future, my future, Y/n must die.

Ridewatch: (Digital beeping) Kyuseishu!

Mitsuru: Henshin.

Rider Time! (Electronic dubstep) Kamen Rid~er Kyuseishu!

Koemi: A Kamen-

Y/n: -Rider...

Savior: Draw your sword, Zi-O.

Y/n: Looks like we're not going anywhere until I beat you. Alright then...

Y/n was about to put on his belt, until Koemi came in and hugged him.

Y/n: K-Koemi what are you...?

Koemi: Don't do it Y/n. This person may really mean it. What if you-

Y/n: Koemi, relax. I'm not going to beaten by the likes of him. Besides, you know me, I've been through way worse. I'll be fine, I promise.

Koemi: ...Okay, but please come back safe.

Y/n: You know I will.

Y/n confronted Mitsuru.

Savior: You shouldn't make promises you can't deliver.

Y/n: But I am making I promise I can deliver. *grabs ridewatch*Now then, bow down to your king.

Ridewatch: (Digital beeping) Zi-O!

Y/n: Henshin!

Rider Time! (Electronic guitar) Kamen Rider Zi-O!

Zi-O: I believe your time... is up.

Savior: Not until I'm finished with you!

Y/n then summoned his weapon and charged at Mitsuru, while he's only walking towards Y/n.

"Zikan Girade!" "Ken!"

Y/n then makes the first strike and delivered a couple of slashes to Mitsuru. But surprisingly, Mitsuru is not damaged at all.

Y/n then attempted to attack again, but Mitsuru hit Y/n with his fist, sending him flying back with tremendous force.

Koemi: Y/n!

Koemi then went to Y/n's side while he's still trying to get up.

Koemi: Y/n, are you okay?

Zi-O: Damm it... Looks like this one will be a tough nut to crack. *gets up*Time to get serious.

Y/n is seen with the Sorcerer Ridewatch.

Ridewatch: (Digital beeping) Sorcerer!

Y/n then inserted in the other side of his driver and turned it around.

Armor Time! (drumroll to downbeat music) Change! Sorcerer!

All of a sudden, Sorcerer's gold color magical portal appeared right above Y/n. As it partially passes through him, it transformed into its proper armor.

Savior: *grunt*You dare to use that dark power against me? I won't allow it!

Mitsuru then summoned 4 physical doppelgangers of himself, which all charged at Y/n.

Y/n then summoned his battleaxe-like halberd and summoned 3 clones of himself from his gold color magical portals. Similar to the Dupe magic.

Y/n and his clones did a fair job in having an advantage over Mitsuru's clones.

Two of Y/n's clones finished off two of Mitsuru's clones with the Blast magic. And one finished off one of Mitsuru's clones by summoning Lightning above it.

Y/n then called back his clones and pressed both ridewatches and turning his driver.

Finish Time! Sorcerer! Strike Time Break!

Y/n summoned a gust of wind that lift him up in the air. Then, Y/n's gold magical portal appeared right in front of the clone. The clone then exploded when Y/n kicked his magical portal with his rider kick at the moment of impact.

Y/n then ran and started fighting the real Mitsuru.

The both of them are equal in combat.

But Y/n rolled and got on the ground after being hit by Mitsuru's two fists, which were charged with power. Y/n was also forced back to his normal state.

Savior: It seems that you are no match for the real deal.

Zi-O: I'm gonna make you regret playing the hero. Alright, how about this one.

Y/n then grabbed Poseidon's Ridewatch.

Ridewatch: (Digital beeping) Poseidon!

Y/n then repeated the same process.

Armor Time! (Shark Orcestra) Same・Kujira・Ookamiuo! Poseidon!

In the middle of the ocean, at the side where Y/n and Mitsuru are fighting, there is a shark, a whale, and a wolffish swimming to where Y/n is. After they jumped out of the water they transformed into armored parts right in front of Y/n before being put onto him.

Y/n then attacked Mitsuru using his armed blade on his right hand, the Hydro Harpoon Z.

Y/n landed powerful strikes on Mitsuru with his blade.

But when Mitsuru attempted to strike back, Y/n's shark head glowed, and suprisingly, dived into the ground smoothly with making a watery splash.

Mitsuru sees Y/n swimming around by seeing his shark fin. But he lost track of Y/n when he dived deeper.

For a moment, Mitsuru was then attacked by Y/n's blade when he emerged from the ground and dived back in again.

Y/n repeated the same process a few more times. Then, Y/n emerged and tackled Mitsuru to the ground.

As both were on the ground, Mitsuru was the first to get up and summoned a giant ball of energy.

After Mitsuru threw it, Y/n's whale arms glowed.

He then impaled his blade to the ground, summoning a giant whale's tail that blocked and send it straight back to Mitsuru.

After Mitsuru was on the ground, Y/n's wolffish legs glowed and it turned into an actual wolffish, with him riding on it.

Y/n then used the wolffish to shoot a geyser of boiling water from its mouth. Which damaged Mitsuru and sended him flying back further.

Y/n then called off the wolffish.

Zi-O: Huh, this armor isn't half bad. Now then...

Y/n then pressed both watches and turned his driver.

Finish Time! Poseidon! Scanning Time Break!

Y/n first jumped into the sky and saw three of Poseidon's medals in front of him. As Y/n performed his rider kick, he pushed and merge the medals into a projection of his armor's chest-plate.

In the moment of impact, the explosion burst out into blue, dark blue, and red flames.

Mitsuru was down on the ground, badly wounded.

Zi-O (Poseidon Armor): You had enough?

Savior: Don't look down on me. I won't be beaten by the likes of you!

Mitsuru then screams and his entire body glows, seeing his wounds restored.

Y/n sighed, then took out the Poseidon Ridewatch and puts it back.

Zi-O: You're really starting to get annoying.

Y/n got out the Bujin Gaim Ridewatch and repeated the process once again.

Ridewatch: (Digital beeping) Bujin Gaim!

Armor Time! (dark modernized Japanese music) Soiya! Bujin Gaim~!"

Y/n's armor appeared above him as Bujin Gaim's face, shaped as a blood orange. After the armor is being put onto the head, it transformed into a deadly shogun-like armor.

Zi-O (Bujin Gaim Armor): On parade, through the shadows!

Y/n then drew his two Bloody Daidamaru Zs and attacked Mitsuru once again.

Y/n whipped up good dual-wielding style combos, and damaged Mitsuru pretty well.

After stepping back a bit, Y/n's leg blades opened up and performing new combos with slashes and kicks. Making it to a four sword-style.

Mitsuru started to get irritated and summoned a giant fist that's about to attack Y/n vertically.

But Y/n's shoulder blades activated and he blocked the fist with and his Daidamarus, resulting in slashing it through.

As Mitsuru ran towards Y/n, Y/n used his shoulder blades to perform two slashes, and then crossed slashed him with his two Daidamaru's.

Zi-O (Bujin Gaim Armor): Time to slice and dice.

Y/n then pressed both ridewatches and turned his driver.

Finish Time! Bujin Gaim! Squash Time Break!

Suddenly, a projection of a blood orange surrounded Mitsuru.

Savior: What is this?

Then, all of Y/n's six blades activated and sliced through Mitsuru three times.

After Y/n did his finishing pose, the blood orange was cut into pieces, and a barrage of slashes was dealt to Mitsuru before exploding.

Y/n then looked at the fire from the explosion, as it looks like it's finally over.

But Mitsuru was seen walking out from the fire, still alive and kicking.

Zi-O (Bujin Gaim Armor): It can't be... How are you...?

Savior: As long as evil beings like you still exist, I will never be defeated.

Zi-O then took out the Bujin Gaim Ridewatch and puts it away.

Zi-O: Well then, looks like I'm going to have to give you the special treatment.

Y/n then takes out the the Zi-O II ridewatch.

Ridewatch: (Digital beeping) Zi-O II!

Y/n then splits it in two-

Zi-O!

-And put both in his driver.

Rider Time! (Dark techno riff) Kamen Rider~! (Rider~!) Zi-O! (Zi-O!) Zi-O~! II!

Y/n then attacked Mitsuru with his Zikan Girarde and Saikyo Girarde.

After a length of fighting, both were about to finish things off.

Savior: Time to end this.

Zi-O II: Couldn't agree more.

Rider Finish Time! Twice Time Break!

Savior - Finish Time! Savior Time Break!

As both riders performed their rider kicks, it resulted in a explosion when landed at each other.

As the dust cleared up, it Y/n who fell on the ground and de-henshined, while Mitsuru was still standing.

Koemi: Y/n!!!

Savior: I am the victor, and now, it's time to end this.

As Mitsuru approaches Y/n, about to deal the finishing blow, Y/n tried to get back while suffering from his bruises and wounds.

Then, Koemi came in and hugged Y/n beside her.

Koemi: Stop it! It's already over, you won didn't you?!

Savior: Move... you're in my way.

Koemi: No, I won't!

Savior: Zi-O will turn into the ultimate evil being who will destroy your world and the future. Why are you protecting him?!

Koemi: Because...! Because at least I know Y/n more than anyone else. You don't know Y/n at all, he would never become anything like you said. And if you still want to kill him-

Koemi then hugged Y/n tightly close to her to comfort him.

Koemi: -Then you have to go through me first.

Seeing Koemi and Y/n, Mitsuru decided to stand down.

Savior: Hear this, Zi-O. I will let you go for now, but only because of your friend there. But the next time we fight, I will not spare you.

Mitsuru then walks into a portal he created and disappeared.

Y/n: *grunt*Kamen Rider... Savior.

To be continued...