I own neither Fate/stay night nor Highschool DxD.

Chapter 2

Angels, Devils, Fallen Angels, and more. Shirou found himself scratching the back of his head after having the fallen angel Raynare spill everything she knew about this world, to her confusion. To think that there were so many pantheons still active in this world; it seemed Shirou had his work cut out for him.

"Who did you say was the leader of you fallen angels again?" Shirou asked, not even bothering to look at the fallen angel he was interrogating.

"L-Lord A-Azazel," a quivering voice responded.

Perhaps he should pay this Azazel a visit, to get the measure of him. Raynare clearly believed that Azazel was the strongest Fallen Angel currently, perhaps even in all of history. If he was to defend humanity, he needed to understand just how powerful his enemies were.

"And the name of your direct superior?" He fired off another question.

There was a moment of hesitation from Raynare as though she was deciding whether or not to answer. He simply looked back into her eyes unblinkingly, causing her to respond in a deflated tone, "Kokabiel..."

It seems in the end that this fallen angel was just a coward. He thought he might've had to torture her for information, but she responded easily and quickly enough. Of course, it also helped that he had traced Fragarach and held it under her throat, preventing her from lying to him.

He gave a small hum in response, "And how do you contact this Kokabiel of yours?"

Raynare's face scrunched up and she gave a glare towards the unamused man, her mouth set in a straight line. Though, he noticed that her lip was quivering anyways.

"Answer me now, or I will hurt you," Shirou stated bluntly.

"As I understand it, your group of fallen angels sends out scum like you to hunt down humans with these... sacred gears. Now, you don't know me but I'll tell you this about myself: I abhor beings like you, who lord their strength over those weaker than them, who threaten humanity. Do you really think I won't make you suffer?"

He watched as Raynare's angry expression fell and she dropped her head, letting out a little sob.

"Forgive me Lord Kokabiel..." she whimpered, "H-he gave me a sheet of paper with a magic circle that would let me teleport freely between his residence in the Underworld and the human world. It's supposed to be outlawed. But, Lord Kokabiel gave it to me anyways,"

Shirou instantly responded, "Take me there,"

She whipped her head up in surprise to look at him, before immediately averting her eyes from his intense gaze.

"Impossible, if they knew I took you, they would kill me," she answered quickly.

He scoffed at her, shaking his head. With a sneer, he said, "Yes, they might very well do that. That being said, if you don't take me to your superior, I will definitely kill you. But I won't make it fast. I'll make you suffer... and suffer,"

He leaned in to emphasize his point. He was confident that with his Presence Concealment, he could likely sneak around the Underworld unnoticed. He was often employed as an assassin by Alaya. Worst comes to worst, he could simply use her magic circle to teleport right out again. Raynare looked up at him again, before her shoulders slumped a little and she nodded in assent.

Though, something about what she said still bothered him.

"Why would he give you something like that if it's outlawed amongst your people," he asked her, curious about the answer.

At that question, her face flushed a light red and she looked away from him.

Ah, that would explain it. So it seems the superior was messing around with his underling.

Shirou quickly followed up, he really had no desire to hear what she was going to say, "Whatever, it doesn't matter. You must've report to him regularly and you must've had to pretend to give a report to him whenever you had your... other visits, no?"

The fallen angel could only give a small and meek nod to his words.

"Good, then everything will be fine if you just do what I say," Shirou dismissed Fragarach and dragged her onto her feet.

Shirou's eyes whipped back and forth as he and his captive fallen angel appeared in a brightly lit lobby in a flash of blue light. The walls had manilla wallpaper with dark marble pillars lining the edges of the room. To his left was a set of large, intricately-carved mahogany doors, and to his right was a sleek wooden desk with a plain brunette woman standing behind it. He knew that she was a fallen angel the moment he sensed her mana and as her mouth started opening, he dashed over without making a noise and knocked her out with a chop to the neck.

He lowered her to the ground slowly as to not make any noise. The agent of Alaya looked behind him to see Raynare desperately covering her mouth, her face as white as a sheet of paper. Right, she was probably surprised by his speed.

He had already told her that once she transported them to the Underworld, she was to stay silent and unmoving no matter what. Now that he was here in the Underworld, he could feel the ambient mana was even more ubiquitous. Furthermore, there were bounded fields everywhere around him, or as Raynare called them, barriers. Some of them were close, like the small one centered around the room behind the set of doors. The others were huge and far away.

Well, it seemed it was a good idea for him to suppress his mana before he was transported here. He did not want to know what would've happened had he been detectable by these barriers.

Walking over to the doors, Shirou felt his eyes narrow as he watched Raynare's expression change from fright to... confusion? Ignoring her odd expressions, Shirou approached the door and reinforced his ears, hoping to catch anything. He couldn't detect any mana signatures in the room, likely because of the barrier around it. Frowning, he realized he couldn't hear anything, maybe it was another function of the barrier. According to his captive, Kokabiel was almost always here since he was a fairly high ranking fallen angel that had many administrative tasks.

It was fine though, he just needed to be in the barrier for a single instance to get the measure of Kokabiel, who was apparently a Cadre-class fallen angel, one of the most powerful fallen angels. He just needed Raynare to open the door while he activated Presence Concealment and entered the room and the barrier. That way, he could understand what he was up against before leaving.

Shirou walked over to her and whispered, "Raynare, open the door and greet Kokabiel as though you were here for any of your other visits,"

"I can't!" she hissed back, "Usually, I'd approach Kokabiel's assistant and she'd talk to Kokabiel before letting me in. I've never just walked in unannounced,"

"Besides, he has his privacy barrier up, he's probably meeting someone right now," she continued.

Shirou grit his teeth together and gave her a deadly stare, "I don't care, just do it. You're concerned for your own life, right? If you don't do this I'll cut you down right now like I did to those other fallen angels and use the magic circle to leave. Or you can do this, and escape with me right after. I need less than a second," he growled quietly.

Once again, it looked like Raynare was on the verge of tears, but still, she obediently started walking to the door. At the same time, Shirou activated Presence Concealment and trailed right behind her.

She grabbed the handles and after taking a deep breath, pushed the doors open. With the doors opening came the voices as Shirou entered the room and the barrier.

"- I don't want the Hero Faction meddling any longer. They've done their part, any- Raynare, what are you doing here?!"

Shirou tuned out who could only be Kokabiel based on Raynare's previous descriptions and instead focused on who he was previously talking to. The gap of power between Kokabiel and Raynare was indeed massive. However, the gulf between Kokabiel and this silver-haired fallen angel was even greater, and his mana was undoubtedly different in nature, different from the other fallen angels he'd met so far. There was no doubt in Shirou's mind that he would have to be a bit careful if he got in a fight with this one in his current state.

Shirou absent-mindedly reached in his pocket to grab Raynare's sheet of paper with the magic circle engraved on it, prepared to simply teleport back to the human world and leave Raynare behind.

It seemed his little visit to the Underworld was educational. There were definitely dangerous existences in the Grigori, but they would be overcome. He dismissed Kokabiel; this silver-haired fallen angel was the more powerful one, but he had faced far worse. Then again, he was powerful, perhaps with senses powerful enough to...

With blazing speed, Shirou abandoned his reach for the paper, and instead grabbed Raynare and threw her in front of himself.

It was just in time to intercept the arm of the silver-haired fallen angel. The only human in the room jumped backwards, reinforcing himself a bit as he let Presence Concealment fall since it was useless now. Raynare let out a cough of blood and collapsed as Shirou watched the more powerful fallen angel extract his arm from where it had pierced through her chest and out her back with a noise of annoyance and disgust.

"Vali, what are y-" Kokabiel let out a strangled growl.

"You cretin, you're like a horny mutt Kokabiel. Your cock led a spy into your ranks," Vali spat, "A human no less,"

Vali lept forward towards Shirou as glowing, bright blue wings sprouted from his back with Kokabiel sprouting five pairs of black wings and forming a spear of light.

In response, the lone human reached out and traced two familiar black and white falchions, batted away Vali's first strike, and twirled around Kokabiel's thrown spear. Letting his instincts guide him, he ducked underneath a powerful kick that was meant to pop his head, instead the silver-haired fallen angel crushed the wall Shirou was against into dust.

At the same time, he whipped his own leg around to kick away another light spear, redirecting it through the ceiling with an audible boom that shook the building. Hopping away from the wall to both open up his mobility and widen the distance between him and Vali, Shirou clucked his tongue in annoyance. The teleportation spell from the magic circle's activation speed wasn't as fast as the silver-haired fallen.

"You fallen angels are starting to really annoy me," Shirou said with a slightly creased brow.

"Ha! You think I'm a fallen angel?"

Before Shirou had time to think about that statement he had to throw up his blades to block a lightning fast punch that Vali sent towards him, "I'm a devil!"

The agent of Alaya found himself skidding across the floor, his feet ripping the floorboards into pieces and kicking up dust from the force of the punch. He frowned to himself as he saw Bakuya chip and crack from that blow. He quickly discarded it and traced another.

"I don't care if you're a fallen or a devil, get out of my way," Shirou spoke with little emotion.

Vali's eyes widened momentarily when he suddenly found himself with cuts on his chest and arm. He was launched backwards through a wall from the force of Shirou's invisible cuts as Kokabiel charged, forming two swords of light.

He turned his focus once more to the dark-haired man and met him resolutely.

Every time their swords met each other, a shower of sparks ignited around them, and the very air shook from the force of their blows. The fallen angel's eyes quickly widened more and more as he found himself first struggling to keep up with his speed, and then actively being forced to retreat over the course of a few seconds.

"I'm being forced back, by a human?!"

The words went completely ignored and as Kokabiel raised his right blade to block a blow, he slid back suddenly from an unseen force.

He looked ahead angrily, only for his expression to melt into pain and surprise. He glanced to his other arm only to see it had been lopped off cleanly at the elbow. Shirou needed to end this one quickly; he felt the other one fast approaching and a two on one battle wasn't in his interests.

The dark haired fallen angel let out a guttural scream of rage as dozens of light spears formed behind him and were launched. The target of his ire fluidly leapt and dodged over every single one and unleashed a monstrous kick to his head.

Shirou himself heard the sound of something cracking and shattering as his foot met skull and ultimately it gave away. Blood splattered on his chest as the fallen angel crumpled and collapsed like a heavy bag, blood pooling around his head.

Letting out a breath, he looked down to see that he failed to properly dodge one of the spears and that there was blood leaking from his side, a gash there. Before he could do something about it, faster than one could blink, he fell into a split and felt the roaring of displaced air from a kick blowing right above his head.

Rolling out of the way, Shirou threw his hand out yet again, letting multiple invisible slashes scatter through where he thought the devil would be. Instead of the sound of flesh ripping and tearing, he only heard the whistle of parting air. He looked up in time to take a punch to the cheek, sending him flying and bouncing through a wall to the outside Underworld.

"DIVIDE!" a resounding voice sounded at the same time.

He felt alarm as his mana dipped an incredible amount. Struggling to his feet and spitting out a glob of blood, he discarded Kanshou and Bakura. Instead, he traced a monstrous sword that seemed more like a slab of stone in the crude shape of a blade. This just got dangerous, if his enemy had the ability to reduce magical output then... wait, his enemy's magical signature had become stronger.

Shirou amended his thoughts, he was a far greater threat than he assumed from before. The ability to steal mana the way he had, he couldn't allow this devil or whatever he was to continue to exist.

His mind was overtaken by steely logic. If his opponent had that ability the entire time, why didn't he use it before? Was it simply he didn't want to, or perhaps there was a different condition for its use? He needed more information. The first hypothesis to test was whether or not there was a range to the ability.

He began accelerating away from Vali, whom he noted had only thin cuts from when he had caught him before with the slashes. It seemed he was quite durable. Shirou broke the sound barrier soon enough and at the same time, began forming swords and launching them at Vali. He ran through what almost looked like a normal human city if it weren't for the people walking around with black wings, the shockwave of his speed blowing many of them into buildings. Vali was slowly gaining on him, he noticed.

This went on for huge tracts of cityscape, and no massive dip in his magical reserves.

"So, you probably have to be pretty close in order to do that," Shirou murmured to himself.

"Stop running you maggot!" Vali spat as he closed in on Shirou, only to startle in surprise as he spun around holding his gargantuan stone blade.

"Sure," he replied and swung.

The silver-haired devil threw up his arms, the blade moving far too fast for him to dodge while he was in motion towards it. He let out a strangled scream as the blade bit deep into his arms. The ground cratered at his feet and his knees buckled. Worse for him, his human opponent whipped around with his fist and buried it in his gut.

Vali was sent flying through what looked like a convenience store to Shirou at Mach 2, a huge dust cloud and sonic boom rushing through the air. He took a deep breath in preparation for what he was going to do.

"That gives me enough time to do this," he said lifting his arms, feeling his mana reserves dip a considerable amount as a veritable wall of steel blades appeared behind him in ephemeral blue motes of light. With a simple gesture with his hand unfitting for the magnitude of what he was about to do, the wall fell.

For a whole minute, the only sound that could be heard for a mile was the sound of metal and rubble. The cracking of the rocky ground shook the earth. The sound of steel clanging on itself, ripping through dirt and stone, and cracking through tremendous force surrounded Shirou.

All around, frightful eyes peaked from behind ruined buildings, watching in awe and horror as countless swords fell from the sky onto a single location, obscured by dust. Screams of fallen angels running and flying away from what looked like a storm of swords were drowned out by the thunderous noises of the blades smashing against each other and the ground.

As sudden as the rain of steel was, it stopped. The one who created it took a deep breath and with a strong wave of Heracles' stone sword, a shockwave blasted away the dust, revealing the fruits of Shirou's labor.

It was a wasteland. Broken shards of steel and rock covered the ground. It looked like a giant had taken a fork and had been stabbing the landscape repeatedly. In the center of it all, knelt the devil.

Light blue ripples of magic surrounded him and slowly faded away. It had to be some kind of defensive magic, though clearly it wasn't completely effective given that he soaked in blood from dozens of wounds small and large.

"You bastard... To think I have to use this on a human," Vali wheezed in pain and humiliation, blood leaking from his mouth as he spoke.

Shirou took a step back in alarm as his mana skyrocketed and some kind of blindingly white armor began forming around him.

"Tch," was the only noise he could make.

Once again, swords upon swords formed and began falling.

In response, Shirou's opponent began chanting.

"DIVIDE! DIVIDE! DIVIDE! DIVIDE! DIVIDE!"

The agent of Alaya found himself shocked and alarmed again as he watched his swords shrink as they approached Vali more and more until they just disappeared outright. Furthermore, he detected something that put him far more on guard than ever before.

Draconic Power

What in the world was going on here? His string of thought was interrupted as out of nowhere, a fist came barreling towards his torso far faster than the devil's previous blows. It was only his Mind's Eye that saved him. Instead of a hole in his stomach, the fist grazed his already injured side.

"DIVIDE!"

At the same time while his reserves were drained again, Shirou swung the great stone blade from Vali's blind spot, catching him in the jaw. The two opponents found themselves sailing through the air in opposite directions.

One wall. Two walls. Three walls. Four walls.

The intruder in the Underworld counted to himself as he blasted through two buildings before stopping himself. He couldn't afford another drain on his reserves anymore. This was a bad spot. His fight had to have started attracting others by now. He didn't even know if he had enough time for it, but reached for the magic circle again...

only to leap backwards with cat-like reflexes to dodge a foot that left a 5 meter deep crater where it landed. Instinctually, Shirou swung at the now armored devil.

"DIVIDE! DIVIDE! DIVIDE!"

Shirou instantly forced himself into a sprint backwards as he noticed Heracles' sword shrink until it was nothing. This was incredibly annoying. Both at long range, and short range he couldn't fight properly with his opponent's ability to just shrink things coming at him into nothingness. His biggest concern was whether or not he could shrink him. He needed a way to distract him and then... Yes, that would do.

His conclusion came at an appropriate time as Vali caught up with him almost instantly and stretched his hand out. In response, Shirou traced a mundane sword that just so happened to be twice as tall as an average man and swung it at his enemy.

"DIVIDE! DIVIDE! DIVIDE! DIVIDE!"

As expected the sword shrunk into nothingness, though he didn't intend to hit Vali with that. He just needed to stall him for a millisecond.

Over and over again, Kanshou and Bakuya were traced. Over and over again, they were thrown, only not all in Vali's direction.

One of the greatest human warriors known to the future, past, and present watched unflinchingly as Vali desperately began smacking and shrinking the swords that were aimed towards him, while turning around constantly, whipping this way and that as multiple pairs of the black and white blades spun in spectacular, unpredictable patterns through the air, guided by the inherent attraction between them.

Shirou didn't let up for a second, constantly forming new ones and throwing them, trapping Vali in a dance with hundreds of blades.

More. More. More.

Until...

At the perfect moment Shirou formed a single blade and shot it through the circling mass of white and black swords. It wasn't directed at Vali himself.

It was directed towards the tip of Vali's shadow.

Vali found himself suddenly frozen and the blades he had been dancing around all disappeared.

The agent of Alaya had caught him with a Black Key of the Church. Its holy power, as he had guessed, was especially potent in freezing the devil.

Still, as a testament to Vali's power, he was twitching along, slowly forcing and tearing his muscles as he turned towards the last remaining blade that had pierced his shadow, the only thing to his mind that could be rooting him in place.

It didn't matter though.

Shirou won.

He didn't know whether or not Vali could or couldn't shrink things while frozen. It was safer to assume that he could. What he did know was that Vali had to react in order to shrink things based on how he hadn't shrunk Heracles' stone sword when attacked from a blind spot.

That was fine though, he just needed something too fast for Vali to react to, and now he had the time to prepare it.

He leapt a great distance away.

"Trace On."

A black bow almost as tall as Shirou appeared with motes of blue light along with a sword thats blade was twisted into a spiral. Nocking it, patterns of glowing blue mana whirled around him, fluttering through his hair. For a moment, the world was calm.

"I am the bone of my sword... Caladbolg!"

The next moment was violence. The air tore and twisted, space itself warping as the Broken Phantasm shunted towards Vali at speeds beyond comprehension, who had just managed to force himself to grab the handle of the Black Key.

The purple sky of the Underworld lit up for miles with a brilliant azure color.

Many who were far away would wonder what caused a blue light to light up the sky.

For those closer to Shirou, they would see fire.

A deafening roar reached him as a magnificently hot fireball tore through the city, vaporizing entire blocks of the city along with its residents. Debris was shot in the air, reaching miles high.

Any other hero from the Throne would've found themselves horrified or proud if they had done what he had done. Shirou though, felt nothing but the resolve of steel. It was time to go, already he could feel the convergence of several magical signatures on his location at blinding speeds, one more powerful than even Vali. That must be Azazel.

He finally took out the slip of paper and channeled his mana into it, vanishing a flash of blue light.

With his departure, he left a whole realm upturned.

Hopefully that was sorta well written fight.