Disclaimer: I don't own Fate/Stay Night or Kamen Rider and they belong to their respected owners.
Shirou has no idea how he got into this situation. Right now, he is standing in front of a man in blue with blue hair holding a red spear. Looks like destiny wants Shirou to fight more than worms and whoever this man is was not human.
"Sorry kid, it's nothing personal," Lancer says. "You just weren't supposed to see me."
"Getting rid of any witnesses, am I right?" Shirou said.
"As I said nothing personal," said Lancer.
"Wait a moment," Shirou raised his hand.
"Are you going to beg?" Lancer raised a brow. "I'm not a fan of beggars."
"No," Shirou shook his head. "You seem like a man who loves a good challenge when facing an opponent."
"Do you have something to face me?" Lancer asked.
"This." Shirou took out a silver object before placing the device on his waist.
SEIKEN SAIKOU DRIVER!
"Hoh? What is this?" Lancer tilts his head.
"I am the blade who will protect this world," Shirou says as takes out a small cyan and gold book.
Kin no Buki Gin no Buki!
He then opens the small book.
Gold or Silver?
Then closes it.
"Now you caught my interest. What is that book?" Lancer asked.
"This is a Wonder Ride Book, left by my father," Shirou replied.
He opens the device on his waist before placing the book onto the device. He then removes the device off his belt, and with a closer look was the hilt of a sword. It also opened the book to a different page.
SAIKOU HAKKOU!
He holds the sword up and says, "Henshin!"
The sword started to glow and Shirou was glowing as well like he was being absorbed into the sword.
Who Is The Shining~ Sword?
The sword was given an announcement as Shirou was fully absorbed by the sword and floated into the air.
Everyone around covered their eyes from the bright glow and when they looked back was not a teen but a sword! The sword had a grey hilt with two yellow triggers inside the hilt and on its bottom. It had a golden blade with turquoise glass on the edge of the front blade. The Wonder Ride Book was on its transformation page and the page had what looked like a figure on it. The figure had a gold star-like helmet with turquoise eyes, a grey body with gold on the right side of it, an X on the center of it, and a small gold X on its waist. He is the Hikari no Ken, he's Kamen Rider Saikou.
SAIKOU ISSHO! KINGIN NO CHIKARA WO ETA KAGAYAKU KEN! SAIKOU!
"Okay, this is now what I expected from you kid," Lancer says.
I am the sword, and the sword is I!" Saikou announced as he took a few swings in the air.
~/~
From afar but close to Rin Tohsaka and her Servant, Archer chased Shiru to make sure he didn't die by Lancer a second time. They saw him losing and was going to save him again but to their surprise, he turned into a sword!
"What the hell?!" Rin exclaimed. "Did Emiya-kun become a sword?! How is that possible?! I've never heard of this before!"
Archer stayed silent but was shocked to see the young teen transform himself into a sword. That is not what he expected and his father gave him this power. Did Shirou's father always have a weapon like this? For now, he looks on and watches.
~/~
"Alright, I don't know how the hell you did that, but let's do this!" Lancer gave a battle-hungry grin.
The second Saikou saw Lancer's foot twist, he sprinted at that floating sword, moving in a blue blur, Saikou readies himself for Lancer's upcoming attack
Saikou grunted, swiping at Lancer with a powerful slash, the blade making a loud whooshing sound in the air. To be honest, this is the first time Saikou fought anybody as a floating sword.
Lancer smirked, seeing Saikou moves coming and deflecting it, before coming at him with a sudden hack. Saikou threw himself about, blocking it and coming out with a thrust at his stomach. The spearman knocked Saikou aside and tried to stab him through the blade's hilt but Saikou dove under Lancer's stab and rolled forwards, and did more dodges from the spear flying over me and spinning before to try to attack Lancer.
Saikou stood up and started slashing at Lancer with all he had, whisking noises being made as he swung himself. Every strike was blocked, Lancer moving with his spear about to block the attacks, as they fought.
"Why don't we try this," Saikou says. "Let there be light!"
SAIKOU HAKKOU!
Saikou charges his sword with ivory energy before he spins and delivers a series of powerful high-speed slashes to the Lancer, the spearman grunted as he was not expecting that attack. It was similar to a Noble Phantasm, the attack left a golden particle upon impact.
Good Luck!
"Well you got me good there," Lancer grunted.
"You were the first person I did that to," Saikou commented.
"Lucky me," Lancer says sarcastically. "Okay now let's end this!" Lancer was about to use his Noble Phantasm, but all of sudden a bright light got between them.
Saikou felt a strange sting on his left hand then heard a strange female voice in front of him, then he saw her.
Saikou saw a young lady of unrivaled magnificence. She was little, and petite around five feet yet that just served to improve her superbness. She wore a blue ball outfit like a dress, yet in a bizarre manner, it was by all accounts flawlessly worked for battle. Over the dress, she wore a brilliant silver defensive layer, silver boots, silver gauntlets, and a silver cuirass in a split second making Shirou realize she was a knight. Her face while the stern was the summit of her excellence and had unadulterated fair hair integrated with a bun, and her face was flawless. Furthermore, her eyes portraying them was a waste of time, they were a profound interminable emerald that appeared to investigate your spirit and made a man need to bow at her feet and swear your essence to her.
'Who is she?' thought Saikou as he looked at the beautiful girl.
"Are you my-" The girl turns to him and stops what she was saying as she took a good look at her Master? "Master?"
"Me? Am I your Master?" Saikou asked.
"Um… you should have Command Seals in your arms…" Saber says.
"Ah… yes I saw that in my arm earlier," Saikou says.
Everyone stayed silent knowing how weird it was talking to a sword, even for a Heroic Spirit and the Holy Grail War, this the strangest thing to happen to them.
AN: This idea was brought on by namikaze93600, I wrote your idea, and tomorrow I will upload Shirou as X-Swordman.