I don't own Fate/kaleid liner Prisma Illya or Kamen Rider and they belong to their respected owners.

"Hyah!" Ryuki slashed Ouja's chest sending sparks and pushing the purple Rider back. "Stop it Uryuu we don't need to fight!"

"You think I'll stop during this festival of death?" Ouja chuckles as he holds up his sword then charges at Ryuki only to be pushed back by Kamen Rider Femme.

"Good, keep fighting Uryuu, it gives more reason to kill you," Femme said as she crosses blade with the Purple Rider.

"Aoko-chan, wait!" Ryuki cried out trying to get her to stop.

"You should heed his warning Aozaki or I'll send you to an early grave as I did your sister," Ouja smirked under his helmet.

Femme growled as she drew an Advent Card and enter it into her Blanc Visor.

SWORD VENT!

Femme gained her Wing Slasher as she charges to fight Ouja, again.

This isn't what Ryuki wanted, he tried to get the Riders to unite and fight off the Mirror Monsters but they have their own ambitions and desires for this Rider War. A Sheerghost was about to strike him behind until a sword stabbed it through its head.

"Emiya, focus!" Knight shouted.

"Mikiya, thanks," Ryuki said to his ally friend. "Look we need to-" Before Ryuki could say anything Knight punch him to the ground.

"I told you before once we enter the Rider War you fight to survive or you die," Knight said.

"But we don't need to fight each other and fight the monsters!" Ryuki said.

"…" Knight stares at Ryuki before both of them jump back as shots are fired in front of their feet.

The two Riders looked up to see Zolda who fired at them.

"You boys should get your head into the game," Zolda said as he enters a card into his Magna Visor.

SHOOT VENT!

Zolda gained the Giga Launcher and fired at the horde of Sheerghosts. Ryuki saw other Kamen Riders fighting like Gai, Tiger, and Verde.

"He's right," Knight said. "I need to win this war."

"I know you want Shiki to wake up and see Mana but you can't risk your life fighting other Riders," Ryuki grab hold of Knight's arm. "You don't want your daughter to learn her father fought as a villain and not a hero!"

"I'll do what I must," Knight tugging his arm away from Ryuki's grasp and charged toward the Sheerghosts

Ryuki let out a tired sigh as he fought the Mirror Monsters and as he looks around the other Riders one Rider caught his eye, a Black Rider, his double, Ryuga. Nobody knows who that Black Rider is but he is strong.

Ryuki ran towards Ryuga while cutting down Sheerghosts were in his way. Till he got close to his doppelganger and called him out.

"Ryuga!"

"Ryuki…" Ryuga said. "We meet again."

"Just who are you?!" Ryuki questioned him as he dodges and slashes at another Sheerghost.

"I'm somebody you already know, Emiya," Ryuga said. "I've been by your side your entire life you just don't know yet." The Black Rider said as he dodged a punch from Ryuki.

"Stop being mysterious and tell me who you are!" Ryuki shouted slashing a Sheerghost before trying to slash Ryuga with his sword.

Ryuga blocked his counterpart's blade and give a dark chuckle.

"You need motivations to fight and win this war," Ryuga said. "Maybe your sister can give you that motivation."

"You leave her alone!" Ryuki growled only to kick in the chest by Ryuga and started to run from the battle.

"Catch me if you can!" Ryuga shouted and left the Mirror World.

Ryuki looked around to see his fellow Riders finishing the monsters or still fighting each other. He wanted them to stop but had to save his little sister. Ryuki ran and followed Ryuga and to save his sister.

~/~

As Illya, Miyu, Rin, and Luvia defeat the corrupted hero Berserker. They were about to head home till they heard a roar. A mechanical black Japanese Dragon burst out from the floor and started to swing its tail and shoot black fireballs at the group of girls. The girls dodge the dragon's tail and the fireballs

"What is that?!" Illya screech.

"It's not a Heroic Spirit, that's for sure!" Rin said as she fired her magic at the dragon.

"It could be a familiar!" Luvia deduce.

Miyu was helping the older girls and Illya was about to help as well but a hang grabs her by the throat. Everyone turns to see Ryuga nearly chocking Illya.

"Illya!"

"Who are you?!" Rin questions him.

"Let her go!" Miyu order.

"One step and I snap her neck," Ryuga said.

"Are you a mage?" Luvia questions him.

"No, I'm here to give him motivations," Ryuga answered.

"Give who motivation?"

Before Ryuga could give his answer sparks came out of his back making Ryuga let go of his hostage.

"I'm trying to help you," Ryuga said.

"I don't need your help!" Ryuki shouted.

"You're in a war you have no reason entering," Ryuga said.

Ryuki clench his fist and glared at the Black Rider under his helmet. "I do have a reason for being in this war!" Ryuki pointed at Ryuga. "I became a Rider to protect the people and Riders. I won't let the Mirror World cause any more death!"

Ryuga chuckled as he took out an Advent Card from his deck and inserts it into his Drag Visor.

STRIKE VENT!

Ryuga gained his Drag Claw with its mouth filled with black flames.

Ryuki also inserted an Advent Card into his Drag Visor as well.

STRIKE VENT!

Ryuki also gained his Drag Claw with its mouth filled with red and yellow flames.

Both dragon Riders thrust their arms at each other as flames shot out of the Drag Claw. The flames hit each other on impact which caused a large explosion covering the sights of Ryuga. As the flames calmed down Ryuga was no longer there.

"He's gone," Ryuki said, he looks back to Illya. "Are you okay?"

"Uh… yes thank you," Illya said.

"Excuse me but who are you?" Rin questions him.

"Yes, I would like an explanation as well," Luvia said.

"Well, I'm Kamen Rider Ryuki but you already know me," Ryuki said.

"Then you're really…" Illya gasped.

Ryuki nodded and removed his Advent Deck making him lose his armor revealing none other than Shirou Emiya.

"Emiya-kun!"

"Shero!"

"It really is you Onii-chan!" Illya gasps when the Rider reveals himself as her older brother. "How did this really become this?"

"Ehehe…" Shirou rubs the back of his head. "Let's say I'm a bit of a spot and I'm trying to save everyone in the city."

"What do you mean?" Miyu asked.

"I'm trying to stop this war with other Kamen Riders," Shirou explained. "The last Rider gets their wish granted."

"Like the Holy Grail War," Rin muttered.

"Huh?" Shirou looking confused.

"So, Shero you join this participate in this war?" Luvia asked him.

"No, no, no," Shirou shooked his head. "I join completely by accident."

"Who was the Black Rider?" Miyu asked.

"Ryuga… but nobody knows who he is," Shirou frowned. "He knows a lot about me. He wants me to join him to win this war… but I don't trust him." Shirou kept frowning till he brought a smile. "So can you explain to me this magical girl look."

Illya blush in embarrassment having her older brother see her in this embarrassing outfit.

"Well, it all started…" Illya began to tell her tale about how she became a magical girl.

AN: After reading Toa Solaric's Agito- Light of Soul and I thought let's try it with Ryuki. It's not much but I'm giving you an idea of what I would write if Ryuki/Fate kaleid became a story.