Disclaimer: I do not own Fate Stay Night, Highschool DxD or anything else.

Fate: Devil Night

Chapter1: Zero Hour

Human World
Japan: Fuyuki
Ground Zero

When he was a child, Emiya Kiritsugu had lived with his father Emiya Noritaka on Alimango Island when his first love Shirley had consumed one of the experimental regents that his father had been working on and was turned into a kind of vampire called a Dead Apostle. She had then drained all of the people on the island of their blood turning them all into ghouls, and he could have stopped it from getting that far if he had killed her just after she had turned. When the Enforcers from the Mage's Association and the Executors from the Holy Church arrived to exterminate the infestation, Kiritsugu had been taken in by a freelance mercenary called Natalia Kaminski after he had killed his father to stop the man from moving on and continuing his dangerous experiments elsewhere.

He spent most his teenage years training under Natalie and had come to regard her as the mother he never had. However after she had been trapped aboard a plane with a Dead Apostle and dozens of ghouls, he had been forced to make the decision to shoot it down killing her along with them. From then on he moved from one battlefield to another, looking for a way to become the hero that Shirley had talked about, eventually picking up his 'assistant' Maiya Hisau along the way.

The Einzberns had approached him them, wanting to reinvent their lost Sorcery Heaven's Feel using a ritual capable of effectively granting any wish which they called the Holy Grail War. He had agreed since he wished for world peace and the Einzberns had given him the Noble Phantasm Avalon to use as a catalyst for summoning of a Heroic Spirit they wanted to fight for him. Kiritsugu had initially agreed and later married Irisviel von Einzbern—the homunculus destined to becoming the Lesser Grail for the ritual. She later gave birth to a beautiful daughters that they named Illyasviel von Einzbern and Chloe von Einzbern.

He'd fought in the Fourth Holy Grail War, a ritual tournament that called forth legendary heroes and villains from bygone eras. They became 'Servants' and with a contracted 'Master' Magus the pair would fight the others until they were the last ones standing. In the Fourth War Kiritsugu had used Avalon to summon King Arthur, a beautiful young woman that was regarded as the greatest of kings, under the Servant class of 'Saber.' He couldn't work with her and had her instead guard his wife Irisviel during the war while he did whatever he could to win it.

He succeeded…

The other Masters and Servants were defeated one by one until Kiritsugu and Saber finally reached the Holy Grail. Maiya had been killed and Irisviel had manifested the true Holy Grail. However all was not as it seemed as Kiritsugu had found out that the Grail was corrupted by Angra Mainyu, a dark god that had been summoned in the Third War. Any wish made upon that accursed cup would bring about nothing but destruction and death. It showed him the 'utopia' that he sought, the complete extermination of all life, leaving only himself, Irisviel and their daughters alive.

He refused the 'utopia' that it had shown…

He made his choice and ordered Saber to destroy the Holy Grail. She had screamed at him, told him to stop, but he ignored her, and used the two Command Sigils that he had left to force her to carry out his order. In the end despite her resistance, she brought down the full might of her Anti-Fortress Noble Phantasm down upon the corrupted Holy Grail. The resulting explosion of ash and dust was immense, followed shortly after by the energy within the Holy Grail—six Servants worth—being unleashed upon the world.

And then the world cracked…

Reality distorted and tore itself apart in an instant. One moment everything was normal and the next the world ended. After a few seconds reality snapped itself back into place and the world just wasn't the same anymore. He didn't know what had happened—he would find out later—but at that moment, the boundaries between two separate worlds came down and merged them both into one. This didn't register until much later, since for now he more pressing concern.

There was fire everywhere…

"No…please no…" Kiritsugu whispered in shock. Looking around he saw that the entire city was on fire now and he could see people dying everywhere. "No!" he shouted as he rushed through the flames looking for anyone that he could save.

He'd brought this disaster by destroying the Holy Grail and would do whatever he could to help those caught up in it. However despite his frantic actions everyone around him died, their lives snuffed out in seconds. Finally after what felt like an eternity he came across a young boy who couldn't have been more than six years old, his hand reaching up towards the sky. He appeared to be badly burned and seemed to be on his last legs, mere inches from death's embrace. Kiritsugu just managed to reach the boy as the last of his life left him, catching his hand before it fell. Kiritsugu had no intention of letting him die and quickly sealed Avalon within him to keep him alive long enough to get him to a doctor.

He was thankful that he could at least save one life in the end…

Kotomine Kirei, the son of the priest in charge of the church in Fuyuki city and former Master of the Servant Assassin stood amidst the destruction that the unborn Dark God Angra Mainyu had wreaked across the city. Thinking about what had happened and laughing with joy as he realises what truly makes him happy is the suffering of others like those in front of him. He laughed at seeing the crumbling ruins and burning inferno that consumed hundreds of lives in a matter seconds.

He laughed at this hell before him…

He'd been selected as a Master for the Fourth Holy Grail War though at the time he had no wish or any real sense of purpose and had only joined the war to find out why the Grail had selected him in the first place. Under his father's and the church's instructions he had allied with Tohsaka Tokiomi who became his mentor who later taught him Magecraft. He later summoned a Servant of the Assassin-class by the name of Hassan-i-Sabah and used him-her-them to do reconnaissance on the other Masters.

Assassin was eventually killed in battle against the Servant Rider and Kirei had spent most of his time conversing with Archer otherwise known as Gilgamesh, the world's first King. Over the course of the war he had become intrigued by Emiya Kiritsugu whom he had originally thought to be like himself only to find out that the man wanted to use the Holy Grail to accomplish world peace, something that went against the very nature of Kotomine Kirei.

Their fated battle took place on the last day of the war and ended in Kiritsugu's victory. Kirei had been killed after the contents of the Holy Grail had been poured onto them both and they had discovered the 'evil' that it contained. He had awoken to find himself alive once more with a black artificial heart connected to Angra Mainyu, the Dark God that resided within the Holy Grail itself. He wished to see what such a being that was inherently 'evil' would do if it were to be born into the world but Kiritsugu had died them both. As vengeance for doing so Angra Mainyu had unleashed this hell upon Fuyuki city, burning everything in its path.

To Kirei it was the most beautiful sight he had ever seen…

"You seem happy, Kirei," Gilgamesh's voice spoke up from the side. He was naked having just been incarnated by Angra Mainyu and the Holy Grail. "Does the sight of this please you?"

"Indeed," Kirei answered with a wide grin as he gazed upon the burning world around him. "I have never seen anything so beautiful before."

"Hn," Gilgamesh grunted with a smirk. "You're far too honest at times, Kirei."

A sudden sound reached their ears, the sound of a child's cry. This wasn't the sound of a child in pain or one that as frightened but one that was surprised. Kirei raised an eyebrow as he looked over at where it originated and saw a single black-haired boy next to a pile of burning debris. The boy was completely unharmed and covered in glowing crimson aura that seemed to be repelling the cursed flames of Angra Mainyu that dotted the area.

Interesting…

"This is…" Kirei trailed off as he approached the boy who looked to be around six years old.

"Have you found something of interest to you?" Gilgamesh mused.

"This boy is unharmed," Kirei commented as he gazed down at the boy. "I wish to see him suffer."

"…What are you planning?" Gilgamesh asked the question.

"…I will adopt him."

Emiya Kiritsugu, the infamous Magus Killer was the greatest assassin of modern times and the 'winner' of the Fourth Holy Grail War. His wife and mistress were lost in the final days of the war, and he had been barred from seeing his daughter ever again by Jubstacheit von Einzbern. To top it all off his body was weakening day by day thanks to the curses of Angra Mainyu, the Dark God that resided within the Holy Grail that had tried to birth itself into the world.

He'd been the one to give the order to stop it by destroying the Holy Grail, and with it his wife Irisviel von Einzbern. Angra Mainyu's revenge against his rejection of it was to set Fuyuki city on fire and use the Holy Grail's power to destroy the barrier between the world he'd known and a parallel world, killing hundreds of people in a fiery blaze of death and despair. Of course Kiritsugu survived it—after all Angra Mainyu had wanted him to know what his rejection of it had caused—and he had combed the devastation looking for someone—anyone—that he could save from the nightmare. He found a single boy, burned and hollow but still alive.

Because of the injuries that boy had sustained, Kiritsugu had been forced to implant Avalon within him in order to repair that damage. Even it was only because of the lingering presence from the recently departed Servant Saber—Arturia Pendragon—that the legendary scabbard was able to heal the boy. Kiritsugu had adopted him soon after and moved into the safe house he'd bought for the war, turning it into a proper home for the two of them.

He named the boy Emiya Shirou…

Despite living at the newly christened Emiya Residence, Kiritsugu made several trips out of the country in order to try and infiltrate Einzbern Castle in Germany. He hoped that he could rescue his imprisoned daughters while the chaos that followed the collapse of the two worlds into one served as a distraction but in the end he failed every time and returned to Fuyuki in a worse state that before he'd left. Shirou had noticed that he was getting weaker as time went on but kept his distance despite his worry over his father's failing health.

It was around this time that he realised something, the Mage's Association was in an uproar, as were the Dead Apostles and everyone else with a foot in the supernatural world. The Age of the Gods had returned, or perhaps it never left? It took a bit of investigating but Kiritsugu had deduced that the discharge from the Holy Grail's destruction had somehow collapsed two worlds into one, and the other world that they had merged with was still in the Age of the Gods. As such gods like Zeus, Odin and Amaterasu were still around.

It was enough to send almost everyone into a panic…

Magi knew better than most what it was like back during the original Age of the Gods, human were treated as nothing more than toys to be played with until they broke. Now the gods had returned and almost everyone was terrified at what that might mean. Not only gods but Angels, Fallen Angels, Devils, and all manner of Phantasmal Creatures now roamed the Earth. It was a small miracle that the existence of Magecraft and the supernatural in general hadn't been revealed to the mundane human populace yet.

Kiritsugu paid it no mind, as far as he was concerned rescuing his daughters from the Einzberns took priority. However since he could not break through the Bounded Fields around Einzbern Castle and his body was slowly deteriorating thanks to the revolting curses which Angra Mainyu had blanketed him with, there was nothing he could do. He'd tried and failed, the only thing he could do at this point was raise Shirou as best he could.

And so that was what he did…

"Illya…" Kiritsugu whispered as he sat at the table. "Chloe…"

"Who's Illya and Chloe?" Shirou asked.

Kiritsugu blinked in surprise for a second and looked over at his adoptive son. He hadn't noticed that he'd spoken aloud and had only realised it after his son had asked him the question. As he looked over at his son's face he saw that the boy was looking back at him curiously, his head cocked slightly to the side as he sat across from him. Was it alright to tell him that he had two sisters? Kiritsugu hadn't been planning to teach him Magecraft despite the boy asking him too but if he told Shirou about Illya and Chloe then he would probably want to meet her.

And he would need to learn Magecraft in order to get to her…

No…

He couldn't put his son at risk like that…

But despite that…

"I was married once," Kiritsugu answered sadly. "Her name was Irisviel von Einzbern…we had two daughters together…Illya and Chloe."

The boy deserved to know…

"I have sisters?" Shirou asked confused. "Where are they?"

"They're with her mother's family over in Germany," Kiritsugu explained bitterly. "I've been trying to rescue them whenever I leave the country but the Bounded Fields around Einzbern Castle have kept me out."

"Can't you save them?" Shirou questioned further.

"Unfortunately you can't save everyone," Kiritsugu answered with a hollow look causing the red-haired boy to stiffen at his words. "I'm going to keep trying of course—they're my daughters—but the chances of getting them out of there almost zero. Knowing Old Man Acht as I do, they're probably being turned into weapons, or worse. And there's not a thing I can do about it," he gritted out as his fists clenched at his side.

Despite being a child Shirou knew that his father was speaking the truth yet he was confused at the strange words his father was speaking. Emiya Shirou was someone who had lost everything in the fire that claimed Fuyuki city not too long ago and had only now started to heal. He'd survived when many others had died and for the sin of living he would save others just as his father had done for him. Now he'd just been told that he apparently had two sisters that were being held captive by the Einzbern family and that they wouldn't let his father see them.

They needed saving…

"…Fine then," Shirou spoke up as if everything was already settled.

"Shirou?" Kiritsugu asked him.

"If you can't save them then I will," Shirou told him. "I don't care if I have to make the whole world my enemy, I'll definitely save them."

Kiritsugu simply stared at his son in shock at his words before a smile slid onto his face, his eyes showing the first signs of life they had in years. Despite having never met them, Shirou had just promised to save them even if he had to make an enemy out of the world. If he had said something like that to the Kiritsugu that existed before the Grail War, the old Magus Killer would have taken steps to stop him there and then despite being his son.

The current Kiritsugu was a different story entirely…

"I see," Kiritsugu sighed and then nodded. "Very well then, I'll teach you everything I know starting tomorrow."

"Thank you," Shirou smiled widely. "I won't let you down, dad!"

You can't save everyone…

But Shirou didn't want to save everyone, just his sisters.

That was all that mattered to him…

The years passed and Kiritsugu trained his son in Magecraft to the best of his ability. He'd never thought of himself as much of a teacher despite having taught Maiya awhile back but as he was helping Shirou learn various forms of Magecraft, he found that it wasn't that bad. He'd taught Shirou all he knew short of transplanting the Emiya Magic Crest onto the boy, and the only reason he didn't was because he wasn't sure if Shirou would survive the process.

"Hey dad," Shirou said as they all sat at the edge of the corridor open to the outside air. "You should get some rest if you're tired."

"Rest?" Kiritsugu chuckled slightly. "Rest can do me no good now."

"Dad…" Shirou trailed off as he looked over at his father.

"I'm proud of you," Kiritsugu told them as he ruffled his son's hair.

They both knew that this was the end…

"Hey dad?" Shirou asked quietly.

"Yes?" Kiritsugu strained to keep his eyes open.

"Thank you for everything," Shirou told him. "You were the best father I could have asked for."

Kiritsugu didn't say anything else, there was no need. He had done everything that he could with the time that he was given, and even if he had so many regrets, he didn't regret raising this child. Idly he wondered if Irisviel and Maiya were waiting for him on the other side before his vision darkened completely. It was then that he saw the image of them both standing in the distance, smiling at him. Even Sherry and Natalie were there beside them. He smiled softly and started walking, his legs taking him forward into the light.

In that moment Emiya Kiritsugu passed away under the moonlight…

Kiritsugu was later given a small funeral organized by the Yakuza Fujimura Raiga and was buried in the graveyard behind the Ryoudou Temple on Mount Enzou. After Kiritsugu died guardianship of Shirou fell under Fujimura Taiga, Raiga's granddaughter and a friend of Kiritsugu's who had recently started teaching at Homurahara Academy, the local high school. Emiya Shirou sat alone in his shed-workshop looking over at the large amount of stuff his father had written down for him to read. Most of it was about Magecraft, Dead Apostles and the Mage's Association, but there was a bit of stuff he had learned about the 'new' supernatural factions out there like the Angels, Fallen Angels and Devils.

He was admittedly wary of the 'new' factions in the world like the Angels, Fallen Angels and Devils but he'd come to realise that if he wanted to save Illya and Chloe then he needed to get stronger. Most Magi were just hiding and praying that they would go away since the 'collapse' as everyone had started calling it. He needed information and knowledge of the world outside of Fuyuki city, specifically the supernatural side of Germany.

He needed to find out everything he could about the world…

That's why he was here in his workshop a year after his father had passed away, sitting in front of the magic circle his father had engraved here ready to summon a devil. He had taken precautions of course—he wasn't that stupid—there were dozens of his father's more lethal Bounded Fields in place around the workshop and they would activate the moment Shirou was about to be harmed in anyway. He hoped that he didn't have to use them but if he wanted information, he admitted that he needed to take a few risks now and then.

Though even he admitted that this course of action might be a tad reckless…

"I hereby announce," Shirou chanted softly. "I have questions and I need answers. Thou, demonic creature from hell, if yee would answer me then hear my words. I am the one whom embodies all the good in this world, I am the one who will vanquish all the evils in the world. Yee devil, appear before me and answer my call."

The magic circle lit up in orange light, flames exploding upwards from it in a blaze. Shirou flinched as the flames flickered across his skin but somehow didn't end up burning him and instead started to spiral around the edges of the magic circle. Finally after what felt like an eternity the flames died down and became nothing more than embers revealing a lone figure standing in the center of the circle. She was a girl a little younger than him with long blond hair and dark blue eyes. Her hair was tied back into a pair of ponytails with large drill-like curls and had blue ribbons holding them in place. She was also wearing a light purple dress with a blue bow at the front and sticking out from her back were two demonic wings made of fire.

This was a devil…

"Were you the one who summoned me?" she asked him. "My name is Phenex Ravel, how do you do?"

She bowed her head and lifted the edges of her skirt slightly like one would expect from a high-class lady introducing herself. Shirou could only stare at her with wide eyes, his mind unable to connect the image of a red demon with horns with the image of this cute little girl in front of him. This was a devil? The enemy of mankind? She looked like some princess from some medieval kingdom! If it wasn't for the flaming wings sticking out of her back, he would have thought that she was a human.

"Erm—I mean—my name is Emiya Shirou," the redhead stammered out. "Hello."

Ravel looked confused for a moment before looking down at the magic circle she was standing in and then around at the rest of the shed. Her eyes narrowed slightly and then relaxed before turning her attention back to Shirou. Had she spotted the Bounded Fields he had in place in case she decided to get violent? The moment he thought that, the flaming wings sticking out from her back suddenly vanished and she took a step out of the magic circle.

"This isn't any kind of summoning circle I recognize," Ravel said gesturing towards the magic circle. "Are you a Magician?"

"I'm a Magus," Shirou answered simply. "I was hoping to find out more about you devils and the other factions out there."

"I see," Ravel mused before nodding. "Very well, can we talk somewhere else? It's quite stuffy in here and wouldn't be a good place to hold an important conversation like this."

"Sure," Shirou nodded and gestured towards the door. "Right this way."

She seemed friendly enough…

Thankfully he had taken the precaution of preparing a few more Bounded Fields over the entire residence as well as the shed just in case…

Ravel Phenex was a High-Class Pure-Blooded Devil and a member of the Phenex clan, one of the seventy-two Pillars. She was also the youngest of the four Phenex heirs, and the only female too. As such she was used to be doted on by her older brothers and her parents, something that she found aggravating at times. She wanted to grow and become her own person, not just 'that girl from the Phenex clan' like many outside of her family saw her as.

She had of course inherited her family's bloodline which was that of the phoenix, a powerful mythological bird with the power to use fire, wind, and even resurrect itself. She was in essence immortal, or at least pretty damn close to it like the others in her family. However she wasn't as strong as her brothers—not yet anyway—and she still had a long way to go before she was anywhere near their levels. As a High-class Devil she had of course been granted a set of Evil Pieces so that she could create her own peerage, her own family.

Since the last Great War with the Angels and Fallen, not to mention their own Devil Civil War, their race had been teetering on the brink of extinction. One of the four Maou—Ajuka Beelzebub—had realised this and created the Evil Pieces system as a way for them to replenish their numbers and survive as a species. What they did was reincarnate other races into Devils and turn them into servants of the Devil that had reincarnated them. Of course many would call it slavery and in some cases they'd be right, but in the end it was for the greater good of all Devil-kind.

That's one of the reasons that she was here…

Originally she had been planning on joining her brother Raiser's peerage as a Bishop since she hadn't wanted to deal with the hassle of a peerage just yet, however that had changes when she realised just how annoying her brother was around his peerage. She loved him dearly but she knew that at his core he was an arrogant, prideful and perverted man. So she had decided to instead form a peerage of her own, though she hadn't actually made much progress on that front yet.

That may change if this encounter was anything to go by…

As a devil she was occasionally summoned by humans hoping to have their wishes granted and their dreams realised. Devils usually did stuff like that to progress in rank and influence both in the Human World and the Underworld. It was considered as a tradition more than anything of course, but it was important, and she didn't mind it much. She had chosen to come to the Human World and operate out of Fuyuki city in Japan, a place supposedly having very little in the way of supernatural beings or anyone really aware of such things.

Imagine her surprise when she found herself summoned by a Magus…

"You're saying that Fuyuki city, the place where I've been living for a year now, is home to not just yourself but at least three other Magicians?" Ravel asked the question.

They'd been talking for hours now, back and forth. Night had fallen and it was getting rather late yet Ravel wasn't planning on leaving any time soon. He'd asked her about Devils, Angels and Fallen Angels, along with the other factions like the Norse Gods and the Youkai. In exchange he had told her about himself being a magician—Magus he called himself—and three others that were living the city. Considering she had been living in Fuyuki for a year already and hadn't suspected a thing, she was rather pissed.

Such was a devil's pride…

"I know that Tohsaka-san is the Second Owner of Fuyuki tasked by the Mage's Association to oversee the city," Shirou answered. "Kotomine Kirei is a priest at the local Church on the other side of town though my father told me to stay as far away from him as I can. There's also Matou Zouken, though he doesn't really leave his family's mansion much."

"I see…" Ravel trailed off as she tried to process this information.

"You mentioned that the Three Biblical Factions are still fighting even after the war ended?" Shirou inquired.

"There's still some conflict between our races," Ravel told him. "But it's nothing compared to the Great War."

The Great War between the Angels, Fallen Angels and Devil nearly destroyed all three races. Out of the seventy-two Pillars of Devil Society, only thirty-four survived the Great War, and those that survived were nearly completely wiped out during the Devil Civil War that soon followed. Most of the Pillars only had one or two heirs these days because most of the branch families that they used to have were wiped out during the Civil War. It had gotten so bad that Ravel's own parents had four children to secure their family's future instead of the one like they had originally planned on having.

The conflicts going on now were all small-scale compared to back then…

"Okay," Shirou nodded in understanding. "I get it."

"I'm interested in what you were saying before," Ravel said with narrowed eyes. "About this 'Holy Grail War' that you mentioned."

"Yeah, my dad was contacted by a Magus family called the Einzberns living in Germany," Shirou explained. "They wanted him to take part of a ritual tournament that they along with the Tohsaka and Matou families had set up in order to recreate the Third True Magic Heaven's Feel. My dad won and obtained the Holy Grail, but it was corrupted and he had it destroyed. The fire that spread through Fuyuki city six years ago was caused by that, not to mention the 'collapse' of our world and your own that followed it."

Ravel couldn't believe her ears, it had been six years since the 'collapse' and 'merging' of the two realms, and the devils had been searching for the cause of it ever since. They had never found anything, and now this boy was claiming that some strange and powerful magic was responsible for it. Not only that but it had happened here, in the city that she had settled in. This entire city was Ground Zero for the biggest event since the end of the Devil Civil War two hundred years ago.

"You're not lying," Ravel whispered.

She could tell…

He was telling the truth…

"I guess that it's a bit of a surprise," Shirou admitted with a sigh.

Yes it was…

"Sign my contract and summon me back whenever you want. I'd like to talk to you a bit more," Ravel told him as she handed him a piece of paper. "From now on you're my number one client, understand?"

"Yes," Shirou nodded and signed the dotted line.

"I'm going home," Ravel said as she stood to leave. "I'll see you tomorrow, Emiya Shirou."

"Good night Phenex-san," Shirou waved as a magic circle formed under her.

"Ravel," she told him as she disappeared. "Call me Ravel."

She was gone a moment later…

"…That girl is going to be the death of me."

Author's Notes:

Hello everyone -waves- I'm back and I have a new fanfic. This one is of course a Fate Stay Night crossover with Highschool DxD starting from the end of the Fourth Holy Grail War. There are some background details that are different than canon-Fate like Chloe presence in the story, and this is intentional. In this story Kiritsugu and Irisviel had two daughters instead of one, Illya and Chloe. As most of you who have read my previous fanfics will know I usually take a well-known starting point in a story and then branch it off in another direction. This ones' is Shirou finding out about Illya and Chloe as well as Issei being found in the fire and being adopted by Kirei.

I hope you enjoy the read and it's great to be back.

Please Read and Review.

See Ya Later…