I own neither Fate/stay night nor Highschool DxD

Chapter 1

Shirou woke up to the barest peaks of orange flame lighting the sky. He painfully picked himself up from the forest ground into a sitting position and remembered his situation. As one of Alaya's greatest defenses for humanity, he had travelled the ages as a timeless warrior serving as humanity's protector. Truthfully, he had not the faintest idea of just how long he had been in the service of Alaya for, he hardly even remembered his own past anymore. He had witnessed countless atrocities and miracles alike, even seeing mankind expand amongst the stars.

Unfortunately, it seemed his service was cut short, given that he had found himself thrown into this forest after he had been called to do battle with another threat to the existence of humanity. Given who he was, he beat it of course, but not before it had done... something to destabilize the very fabric of time and space, causing a rift to form and drawing Shirou into it.

It was that very rift that had taught Shirou pain again. He felt the unbridled strength of Alaya leave him, their connection ruined at best, and was sent thrashing into a void of maddening color and feeling. Time lost meaning, there was only pain... until he found himself dropped into this forest.

The first thing Shirou had noticed after properly taking note of his situation was the ambient mana of wherever he had been deposited. To put it simply, it was far more pure and prevalent than the mana at any point in time on Earth or beyond that he could remember. It was shocking enough that he found himself in a cold sweat. This kind of ambient mana, he didn't like what it implied. The worst option that came to mind was that he was in a world that was still in the Age of the Gods. The very thought of it made him recall the wanton cruelty of careless gods that he had faced.

He frowned to himself and with a little difficulty, stood up all the while still expanding his senses further to see if he could detect anything more.

After a quiet moment, he whipped his head in a full 180 degrees when he noticed some kind of large scale bounded field two miles behind him. With a meager application of his mana that he could still muster for reinforcement, he broke out into a sprint in the bounded field's direction faster than most people could even see.

As he pulled closer to the bounded field, he quickly slowed down as he realized he was outside some kind of town. The architecture gave him an odd feeling of familiarity that he quickly brushed off. Ignoring the looks he received from the few people milling about, he walked into town to find the nearest place he could find information from.

Shirou found himself walking into an internet café, if his memory was correct, and sat down in front of a computer. After some fiddling with the buttons, he managed to turn it on and opened an internet browser. He had already known he was in Japan based on the signs and people as well as a rough idea of what possible time period he could be in based on the architecture and clothing. After browsing through the internet, he quickly concluded that on the surface, this seemed like a very common alternate Earth. There didn't seem to be any evidence of magic on the internet, despite him being in the center of a bounded field that he hid himself from by greatly suppressing his mana. Furthermore, he found many historical events that he had definitely heard of before. He even now knew the name of this town: Kuoh.

The former agent of Alaya found himself briefly overcome with a strange feeling. Slowly, he typed two words into the search bar and hesitated over the enter button.

Fuyuki City

He pressed the button and watched as the search engine returned no results. Shirou felt an odd pain in his heart before he quickly stamped the feeling down. He had no idea why he did that, what was that city? It wasn't important. He had bigger concerns.

He was ultimately a guardian of humanity, whatever it was he just felt, it didn't matter. Nothing mattered but the objective he had dedicated everything to.

"Sir!"

Shirou suddenly jolted in his seat and reached up, grabbing towards the sudden intrusion to his thoughts.

"What the!" the feminine voice yelped in a strangled voice before being cut off.

Shirou blinked and felt his grip slacken as he realized he just spun out of his seat and grabbed what looked to be an employee at this internet café by the neck. If he had realized what he was doing any later, he likely would've popped the poor girl's head right off her neck. He quickly dropped her and backed up slowly, watching her lay on the ground coughing.

Before anyone could stop him for his sudden violence, he took off from the café.

Shirou frowned to himself as he once again failed to make any kind of contact with Alaya. It was odd, to think that a seemingly normal Earth such as this had no connection to Alaya despite how many humans were milling about. There shouldn't be any reason Alaya wouldn't have influence on this world. A thought stilled him for a second, before he looked around to make sure no one was watching.

Discreetly, he traced a simple knife and watched it intently.

His eyes widened as he realized that he had no need to keep the traced knife's form solid with a constant stream of mana. This could only mean that Gaia itself wasn't even present on this world to suppress all unnatural phenomena. He once again suppressed his mana and left with no destination in mind.

He realized that he had no idea what to do. For the first time that he could remember, Shirou felt as though he had no purpose. He found himself on his knees, looking aimlessly at the clear blue sky.

He had given up more than he could even remember to pursue his ideal. How much did he lose? He ignored his own question, he just knew that he had to protect, had to guard humanity against all that would threaten it, even if humanity itself was the threat. Without Alaya's directions and power, he was stuck on this Earth, with a fraction of his power and nothing to turn to. There was no threat that he could see, no danger that he could point himself to.

It felt all so pointless now, the sacrifices. He had forgotten more faces than anyone would ever meet, he couldn't even recall... whose face? There was someone, someone who he thinks might've been important to him in the past.

Ah, why was he all of a sudden so introspective? Why did it feel like he was sinking? When was the last time he had even had a break from his time in between disasters, wars, and the countless dangers all possible humans have faced?

He needed to occupy himself, he couldn't think, couldn't look back. If he did, he was lost.

It was in this moment that he felt a small, brief surge of mana. Shirou stilled, his entire body a statue. His mind ran a thousand miles a minute, and could only come up with a single word.

Inhuman.

Whatever that surge of mana was, it was distinctly non-human. Of course, he was a fool, just because he was separated from Alaya without the ability to travel endlessly from battlefield to battlefield didn't mean his purpose was done. There was clearly magic in this world, of course there would be threats abound to humanity here. He had let himself be deceived by the normality of what he had seen so far in this Kuoh and on the internet.

He felt himself finally calm down and his mind of steel regain strength. Yes, of course, what had he been thinking, he had clearly been staring at clear evidence that there were possible threats to mankind in this world. There was a bounded field surroundings this very town, and ambient mana levels fitting for the Age of the Gods. He needed to investigate all there was to see in this world, to find what lurked behind the perception of common humans.

With his last thoughts of self-affirmation, he quickly sprinted off towards where he felt the brief surge of mana.

Shirou arrived under the light of the moon to a bloody scene, something that didn't even faze him at all. A brown-haired boy who looked to be in a school uniform was lying in a pool of his own blood, very clearly dead. This place, now that he stood in the center of it, reeked of some kind of inhuman magic. How had he not felt it clearer when this boy's death had happened? Perhaps the thick ambient mana made it harder for him to sense things properly, or maybe it was the bounded field. Either way, this sight simply confirmed his thoughts and solidified his steel resolve.

Something's magic had just killed a human here. Looking at the ground, he noticed that whatever had done this had done a very poor job of covering their tracks. He could easily track the direction they went after killing the boy just by the residual mana. Normally, Shirou's senses were incredibly keen at detecting mana, but in this world, if it weren't for the fact that he was standing right at this very spot after the use of magic, he wouldn't have even noticed any residuals at all. He narrowed his eyes as he began following the trail left behind.

The agent of Alaya continued following the shoddily covered residuals all the way to a seemingly abandoned church. Its gates were covered in vines and the building itself was in poor condition. The walls were cracked, with large swathes of the walls with no paint left. He also took note of the cracks in its structure.

How very typical, for supernatural elements hidden from human eyes to be found at some abandoned building.

With barely any effort, he jumped the gates and trudged on to the church's entrance. As he got closer and closer, he slowed down more and more. He could tell there were four alien mana signatures, all underneath the church, but he could also detect the magic of humans in the actual building. They couldn't be mundane humans, their mana was too strong for that.

Humans were working with these entities? Given that they simply left the body of the boy they killed out in the open to rot, he didn't particularly think these people and whatever they were working with were friendly. Perhaps he should just listen in and go from there.

Shirou reinforced his ears while standing right against the door.

"- Jeez, I hate having to deal these cocky fallen angels, always looking down on us,"

"I just want to get out this damn building. It's nasty,"

"You're damn right, I can't fucking wait for this job to be done,"

The agent of Alaya narrowed his eyes at the new terminology. Fallen Angels? That could be concerning. He had many experiences with beings that would call themselves angels, many of them extremely powerful. He didn't think the beings below the church were that powerful though, their mana didn't seem so strong. They also didn't seem to be suppressing their mana at all strangely enough. Really, it didn't seem like any of these people were suppressing their mana. He wondered, why that was. The magi he had become familiar with all suppressed their mana in order to obscure knowledge of how powerful they were out of battle. Only the extremely powerful usually let their mana loose, a sign of their strength.

However, these people and the so-called fallen angels were nothing like that. He was missing some information here. He once again wondered about the function of the bounded field that covered the town. He had no idea what it did so far. It was entirely possible that the people in this church were responsible for it.

He focused back on the conversation in the church just in time to hear one thing.

"Don't worry, the nun will arrive soon, those fallen angels will extract her soul, and we'll be free again,"

Upon hearing that, Shirou had heard enough, he straightened his back, lifting his foot, and after reinforcing his body, kicked open the rickety doors of the church.

"What the fuck!" a white haired man in some kind of ornate black overcoat yelled, his eyes wildly swiveling to see Shirou walking through the shards of wood and dust left behind from his kick.

Shirou himself took note of the humans all standing around in various states of shock. They all seemed to be wearing similar black coats with some kind of white uniform underneath. They all scrambled to ready their weapons: firearms and.. glowing swords?

Shirou gave them all a dead stare that conveyed nothing but apathy.

"All of you drop your weapons and answer my questions, or I'll kill you all," he ordered blankly. His voice betrayed no feelings whatsoever. It was as though he was a robot uttering a pre-written line. He honestly didn't have many expectations for these humans. They were clearly much weaker than the beings under the church and subservient to them. It was likely that these people were fodder.

He listened to the white haired one give an unhinged laugh, "Are you kidding me, who's this idiot? Let's kill him!"

Shirou felt nothing but annoyance as the white haired man's lackadaisical words seemed to invigorate the others to get over the shock of Shirou's entrance and get ready to attack him.

Whatever, it was fine. Even in his currently weakened state and wounds from before arriving here, these people were chaff in the wind to him.

Shirou simply concentrated on the magic inherent to him: his Unlimited Blade Works. As he was, he honestly wasn't sure if he could even manifest the full reality marble, but it didn't even matter. He focused on the barrier between normal reality and his reality marble, carefully breaching it. This was a trick he had picked up long ago, it was a very useful attack as to most people, it was undetectable and generally kept his abilities secret.

As the humans in the church began to attack. Some walking forward with their blades and others taking aim with their firearms, Shirou allowed just a sliver of his blades from Unlimited Blade Works to slip through reality, whizzing towards his enemies.

To the outside viewer, there was a sound of something tearing and fraying, and invisible slashes ripped through the people in the church, leaving large gouges and collapsing some of the walls.

Shirou stood still as blood flew. All around him, some of his would-be attackers fell apart into neat slices, staining the ground crimson. Others suddenly found themselves pushed backwards, their limbs detached, or simply with huge fatal cuts.

He could hear the people who managed to survive at first screaming and yelling at the top of their lungs. The church shuddered, dust and debris filling the room as the aftermath of Shirou's attack left its foundations cut and even more ruined.

Looking up, Shirou decided it seemed his control wasn't as good right now given his injuries. He simply intended to carve up the humans, not leave the church's roof teetering on collapsing inwards from the slashes.

After the yelling was just the gurgling of doomed men. Every single one either dying from blood loss or being sliced into pieces. The walls and floor were all red and a metallic scent clung to the air, leaving Shirou the lone person standing, totally unfeeling of the carnage he had just unleashed. The number of people he just killed didn't even register in his mind. His focus was turned to the mana signatures under the church rushing up.

He got an eyeful of three women and a man sporting pairs of black wings. But their features were ultimately meaningless, he judged them as non-threats to himself. And, after tonight, they would be non-threats to everyone. He noticed that none but the smallest one didn't seem to react with any pity or sadness to the dead humans, though they all seemed shocked enough from the widening of their eyes and the drooping jaws. The smallest one turned around and promptly vomited on the ground, retching on her knees. Perhaps she was just queasy then.

"Wha- how- who are you?! What have you done?!" one of the female fallen angels stepped forward, demanding. It seemed to Shirou that she was their leader.

"I offer you the same choice as them, answer my questions or die," Shirou ordered with the same monotonous tone.

"Tch. Don't get cocky! These humans were all weak, you think you can look down on us?" the man growled, stepping forward as well. His single step doomed him. The fallen angels were suddenly blasted on their backs. They turned to see their male comrade's legs collapsing on the ground. Shirou heard the fallen angel that was vomiting promptly begin screaming as she realized that the male fallen angel's upper torso was spread apart further behind in a series of bloody, sliced chunks. Shirou looked up, hearing the church's ceiling making a groaning sound, it seemed it couldn't take anymore of the cuts he had left in its walls.

"Kalawarner! With me!" the female fallen angel called wildly to the only other female fallen angel that wasn't laying in a puddle of their own vomit. They formed spears of lights in their hands, but before they could charge or throw the spears, the one named Kalawarner also fell apart into neat slices, leaving nothing but the sounds of her gushing and splattering blood, the spear she formed fading into nothingness.

"Last chance," Shirou uttered.

"Wait... wait... please don't hurt me. I'll comply! I'll comply!" the supposed leader shrieked hysterically, her spear completely forgotten as she threw herself onto the ground, her head pressed against the floor in fear.

Shirou considered her for a moment, and after deciding that she seemed suitably cowed began walking forward. The small blonde fallen angel was still yelling, not able to process the bloody affair that just occurred in front of her.

"Are you the leader of this bunch?" Shirou asked calmly, a distinct feeling of faint disgust coming over him staring at these squabbling bunch of feathered beings that called themselves fallen angels.

"Yes! Yes I am! I am the leader of these fallen angels, called Raynare! Please don't kill me! Please! Please!" the now named Raynare begged piteously.

"Calm down. Does your last companion know anything you don't?" Shirou continued while staring at her.

Raynare looked up at him confusedly and with fear clear in her eyes before responding quickly, "No! No!"

Her eyes bulged even more as the tearing sound came back and Shirou watched her eyes slide over to witness the small blonde fallen angel's head come flying off with a spurt of blood and a clean slice to her neck, stopping her screaming abruptly.

She let out a strangled sound and slowly turned her head and looked up to Shirou's steel-colored eyes, completely frozen in fear. The church was completely silent now. It was a jarring contrast between the previously worn down church, now covered in blood with gouges covering the walls and body parts strewn about.

"Good. Now I want you to answer everything I ask honestly, do you understand?" Shirou asked, crouching to be eye level with her.

I've decided to rewrite a super old story called A Sword's New Adventure. Not that there was much to rewrite.