Disclaimer: I do not own World's End Harem: Fantasia or Kamen Rider and they belong to their respected owners except for this one OC.
Āku Nagara was just a young man of a noble branch family before gaining power, he was mocked for being weak and was unable to marry somebody he loved. That was until he met the Dark Elf Latifo Leozard who offered him power, Āku was hesitant but accepted it not wanting to be weak.
Crazy enough, Āku had gotten stronger but what really gave him power was the liquid in his body like; blood, saliva, and semen which gave him power over women and them wanting him. After a while, Āku was able to protect his family even when his father got ill, but what surprised him, even more, was the new power he received.
Latifo handed him a small purple plastic book called the Jaaku Dragon Wonder Ride Book. And when took the Wonder Ride Book, it activated a power that was hidden and lost for a century. It was a sword with a yellow jagged blade and a purple hilt. Āku can feel the power coming from the sword.
Latifo told him it was a Holy Sword that held great power, the sword was called Ankokuken Kurayami, the Darkness Sword chose Āku to be its next wielder, to become the Dark Swordsman. Āku was hesitant but Latifo reassured him that the sword won't change who he is, it only matters to the warrior who wields it.
Now, Āku is the snow trying to assist the Grand Duchy of Gautier Cassia Weskey in fighting a large white monster. And even if he gave Cassia some of his blood to give her a power boost the white monster is still strong. So the one thing he could do and that is to henshin.
Āku wore his belt known as the Jaken Caliburdriver and was placed on his waist. He held his sword Ankokuken Kurayami with his right hand and held a small purple book with the other. The small book was the Jaaku Dragon Wonder Ride Book. He held the book showing an image of a purple dragon on the cover.
JAAKU DRAGON!
Āku opens the Ride Book showing its Story Page.
It was only one beast, which birthed the darkness that once enveloped the world.
He closes his Ride Book before scanning the Jaou Dragon Book on the Ankokuken Kurayami.
JAAKU READ!
Āku then places the Ride Book in the Jaken Caliburdriver slot and says, "Henshin." And presses the button on the top of the Driver with the bottom of the sword's hilt.
The Jaaku Dragon Wonder Ride Book appeared behind Āku, the large book flipped open with a projection of a gigantic, purple dragon coming out of it.
ANKOKUKEN KURAYAMI!
The purple dragon swirled around him as dark energy form around Āku
GEKKOU! ANKOKU! ZANGEKI! JAAKU DRAGON!
Āku sliced down the Ankokuken Kurayami making him from his Calibur armor.
KURAYAMI HONYAKU! HIKARI O UBAISHI, SHIKKOKU NO KEN GA REIKOKU MUJŌ NI ANKOKU RYŪ O SHIHAI SURU!
As the dark energy disperse, people, get to see Āku in his new armor, the people around him can see how imitating Āku's armor looks, they can even feel the dark energy coming from it.
Āku was wearing a suit with purple that goes down to his feet in the middle, as well as black parts on his side torso that goes all the way down to his feet, his arms purple with black parts on the side with gold lining, black collar with gold lining, and a long black trench coat-like with gold lining covering his right leg. Silver armor chest and on his left is a shoulder pad with studs on it while on his right shoulder is a dragon head, and in the center of his chest is a golden blade jagged edge. The helmet is black as in the center of his forehead is a purple part and a single golden jagged blade-like horn and a silver visor are studded with two red linings holes. He became the Dark Swordsman known as Kamen Rider Calibur.
"What is this power?!" Cassia questioned.
"The power of the Dark Swordsman, Kamen Rider Calibur," Wenna answered Āku.
"Calibur… I thought that was a myth." Cassia looks at Calibur. "Then that means…" She set her eyes on Kurayami. "... That sword."
The white monster jumps forward, sending the first strike with his sword. Calibur noted as he dodges the horizontal strike of the white monster, noting how wild some of the monster's strikes are. Calibur brought his sword up to give the white monster more strikes on its body.
The Dark Swordsman had a hard time blocking all the attacks, but he managed somehow to survive the barrage of sword strikes. After a few seconds, Calibur jumped back while sending a slash at the white monster making the giant beast stumbled back before managing to regain his balance just in time to block a strike from Kurayami.
The Calibur lifted his weapon and swung his sword with precision and speed, able to block and parry the strikes from the white monster. Through several strikes, Calibur managed to strike against the large monster. Both backed away, smoke coming from strikes to their torsos.
"Why don't we try this." Calibur then proceeds to remove his Jaaku Ride Book from his Caliburdriver, he then scans the Wonder Ride Book at the base of his blade.
HISSATSU READ! JAAKU DRAGON!
Kurayami was covered with dark energy as Calibur pulled his weapon's trigger.
KURAYAMI HISSATSU GEKI! SHUUTOKU! SHUUTOKU ISSEN!
Calibur shoots out a group of black dragons that were homing at the white monster and restraining the giant beast.
"What?! I can't get out!" The white monster cried out.
"Yes, this is where you meet your end," Calibur says as he scans his Wonder Ride Book at the base of Kurayami's blade three times.
HISSATSU READ! HISSATSU READ! HISSATSU READ! JAAKU DRAGON!
Kurayami's blade begins to charge with darkness energy before Calibur then pulls his weapon's trigger.
KURAYAMI HISSATSU GEKI! SHUUTOKU SANSEN!
Calibur charges Kurayami with dark energy before he delivers a powerful slash at the white monster, truly ending the white monster.
"Gahhh!" The white monster screamed as his whole body was engulfed into an explosion destroying the monster's body.
Growls were heard behind Calibur, he then turns to see Devil Wolves before the Dark Swordsman sheaths Kurayami into his left-hand Hissatsuholder before pulling the trigger, he then pulls the sword back out.
KURAYAMI IAI! DOKUGO ISSEN!
Calibur held up Kurayami as dark energy surrounded the blade charging it before pulling the sword's trigger. Calibur did a downward slash enhanced by dark energy and released a power slash field with nothing but dark energy slicing through the Devil Wolves and killing them.
"Nagara." Calibur turns to see Cassia looking at him before bowing. "I would like to thank you for your assistance."
Calibur bows his head as well, "There's to thank me yet, I would love to help save your country from this black death."
Cassia nodded, "If you will assist me in helping my soldiers up, we can work together."
"It would be no problem at all," Calibur complied.
AN: If you don't know what World's End Harem: Fantasia is, well it has nudity(Only with breasts), extreme ecchi so it has sex scenes. I remember reading a chapter where Āku became reincarnated as a revered Black Dragon by Latifo and I thought of Kamen Rider Calibur. Also before you say anything, this one-shot is the World of Calibur so there aren't any other Riders... for now. I hope this one-shot caught your interest.