Prologue

Hello everyone and welcome to another interesting crossover requested, and beta read, by Steeler Steelix and Pyromania101! This time we have a crossover between the Highschool DxD fics 'Go Away I'm Watching Porn' and 'A Demon Lord's Hero'. Will the two protagonists mesh well, will they hate each other, will Issei get to watch his porn? Whatever the outcome it's sure to be chaotic for all involved.

I learned a lot of things during the 5th Holy Grail War. I learned how to fight, how to really wield magic, how to better protect myself and those I cared about. At least, I thought I had learned how to better protect those I cared about.

But it was now as I knelt within my ultimate magic, Unlimited Blade Works, holding the still and slowly dying body of my beloved sister, Illya, that I realized how powerless I still was.

'It's not fair,' I had thought. I might not have done everything right, but I stopped the ones threatening the world, I protected those I cared about. Why does Illya have to pay for other people's mistakes?! I was doing everything I could think of. I had picked a location strong in magic, drawn up a complex magic circle that I triple-checked and even brought her here, to my Reality Marble, in an attempt to get the magic to work faster.

But none of it was working! No matter how much Mana I imbued into my sister's body, no matter what mystical weapon I summoned, no matter how much I begged and pleaded, my sister continued to slowly die in my arms. Archer had told me that this was just how things were gonna be, that as a homunculus Illya's life was going to be short, especially compared to the life of a normal person. But I didn't want to accept that, no, I absolutely refused to accept that!

So I cried out with all the pain and anguish I was feeling in that moment, begging and pleading for any entity—be it a deity or a demon that was listening. And to my actual surprise, someone was listening.

The next thing I knew, a red magic circle appeared in front of me as a girl emerged, dressed in a pink magical girl outfit with long black hair flowing down her back.

"You want to save your sister?" She said in a sweet voice that belied her true nature. "I can help, but there's something you should know."

"Whatever it is you want, I'll give it to you." I had said without any hesitation, already anticipating that there would be price for this miracle.

"You say that now," the girl had purred in amusement, "But what if I told you that I am a Devil? And that the price for saving your sister…will be your soul?"

"Deal." I replied instantly and without a second thought. "Take whatever you want, just help Illya."

"Wow, not even a hint of hesitation." The Devil girl praised. "Alright, allow me to show you some of the magic of resurrection from my world."

She knelt down then and examined Illya. I didn't know it at the time but she was reading the movement of Mana within her body as well as trying to figure out its composition.

"Hmm, this will be slightly more tricky than a normal resurrection, but still doable."

The magical girl Devil waved her hand and summoned a red Rook piece.

"What's that for?" I asked upon feeling the magic from the chess piece.

"This is one of the many things you're going to learn about." The girl replied before waving her other hand over the piece, causing it to glow in her palm for a moment. "But to put it simply, this is an Evil Piece. I had to mutate it a bit for your sister here, but it should work now."

She then proceeded to press the red piece against Illya's body. It began to glow before sliding into the spot where her heart should be.

"Now, celestial forces," the Devil girl said dramatically while twirling her wand, "Bring this little one back home!" She pointed her staff at Illya.

"Uh," I replied unintelligibly, "Is all of that really necessary?"

"Necessary?" She replied with a smile. "No, but everything is better with a little 'magical girl' in it."

I might've argued the point and phrasing on that, but it was at that moment that Illya let out a little yawn and her eyes slowly opened.

"Shirou," the white-haired girl said, "Why is it so noisy? Illya is sleepy right now."

I just stopped myself from yelling in surprise as I quickly checked her pulse. Her breathing had returned to normal and her heart rate was strong again. I choked back a sob as I realized that she wasn't dying anymore. It also dawned on me that she now, at last, had a chance of living a full, complete life.

"S-Sorry, Illya." I said as I tried and failed to keep the tears out of my eyes. "We're just…fussing over nothing right now."

"Okay," she mumbled, "Illya will sleep now. Daytime too bright."

The small girl shifted slightly before her breathing steadied. It took her no time at all to fall back asleep.

"Thank you." I said as my gaze returned to our savior. "I was…honestly at the end of my rope. If you hadn't come along I…oh that's right, I never asked for your name."

"Oh right, with all the drama I forgot to introduce myself." the Devil girl said excitedly as she again twirled around her wand before spinning dramatically and striking a pose with her two fingers in a sideways 'v' sign. "I am one of the 72 Pillars. A Maou of the Underworld as well as one of its strongest!" She pointed her wand upward. "The eldest sibling of the Sitri family, I am Serafall Leviathan!"

"Serafall…Leviathan." I repeated before bowing my head. "Thank you."

"Uh-uh-uh." She shook her finger before grabbing my chin and lifting my head up so that I was looking her in the eyes. "Don't thank me yet Mr…Shirou was it? You still have your end of the bargain to uphold."

"Right, you'll be needing my soul now." I recalled. "Just give me another moment to say good-bye to Illya, if that's okay?"

"Now why would I do that?" Serafall asked with a smile. "I'll have you know, I have a little sister myself and absolutely abhor the idea of separating two siblings, especially now that one has a chance at a new life. So save your good-byes for later because I'm taking you both back to my world."

"But the deal was—" I started to protest before the Maou held her hand up to my face.

"Relax, I'm not taking you both to suffer eternal torment." She explained. "I'll be taking you both to a parallel world that is different in many ways from your own. But first, I'll need to get to know you a little better."

She looked me in the eyes with her violet orbs before they turned crimson, and I felt her presence within my mind—my very soul!

Images flashed across my vision: the great Fuyuki Fire, my rescue by my adoptive father, Kiritsugu Emiya, my first lessons in magecraft, my meetings with people like Sakura and Taiga.

Then they came faster as I watched it play out again. The Holy Grail War, meeting the sister I had searched for, my summoning of Saber, my first meeting with Archer and Rin, the numerous battles against powerful opponents, the hard-fought victory, until it all finally led back to this moment.

And just as suddenly as it had begun, it was over.

I looked around, noting that we were still within the confines of my Reality Marble. But there was one change I took notice of: Serafall's face had gone from one of amusement to one of…shock, possibly.

It was as if she didn't quite comprehend what she had seen.

Then, ever so slowly, her body began to shudder until the trembling reached her mouth. And then a small laugh escaped.

It was like a switch had been flipped as Serafall threw her head back and began laughing and laughing, so long and loud that it seemed to fill up the whole area of my Reality Marble. It kept going and going, as if it wouldn't end for hours.

Yet, despite the evil creature she was supposed to be, there was nothing malicious about her laughter.

In fact, it was joyful and pure as if her voice was a ray of sunshine after a long storm. And I realized that it had been a long storm for both of us. Maybe that's why I joined in her laughter. Our tired souls had finally found relief.

"At last." She said, looking at me while tears of joy fell from her eyes. "I finally found you at long last."

"I don't know what you mean." I replied. "I'm just happy to see you smiling."

"Just what I would expect from a Hero." Serafall commented with a giggle. "I didn't realize it myself until just this moment. This will be hard to understand at first, but I've been searching for a long time now. All over my world, I had searched and not so long ago I had given up searching, deciding it was hopeless. Or so I had thought."

She smiled happily as she continued. "But I see now that I was looking in the wrong place. You see, Emiya Shirou, you are a miracle, a miracle I've been searching for. Not since my Evelyn or my little So-tan have I felt what I feel for you. I know this is forward of me, but I'm not interested in wasting chances this time. So I'll come right out and say it: I love you."

And just like that, my brain went from absolute joy to complete short circuit.

Later: The Underworld

"Alright, let me give you the rundown!" Serafall announced cheerfully as I felt my chest where she had put a Queen piece. "What I've just put in your body is a Queen piece. From this moment on, you're no longer a human being but a Devil."

"To be honest, I don't feel that different." I replied while examining my right hand, giving it a few experimental flexes. "Am I supposed to be like you now?"

"Yes and no." The Maou replied with a raised finger. "What you are specifically is a Reincarnated Devil. As the name implies, you have been changed from a human to a Devil."

"Are you saying I died?" I asked with a raised eyebrow. "I mean, it wouldn't be the first time I 'died', if we're being honest, but that didn't feel like dying just now."

"Well, the process is often used on dead humans as well as living." Serafall explained. "So we just started calling Devils like you Reincarnated Devils."

"Then what kind of Devil does that make you?" I asked. "You mentioned the part about being a Maou."

"I am what is known as a Pure-Blooded Devil." She replied. "I've been a Devil since the day I was born." The ten black wings protruded from her back again. "And in case you haven't guessed, I've been around for a while."

"Okay." I said. "But if there are already Pure-Blooded Devils, why have Reincarnated Devils? Is that just what you do when someone sells their soul to you?"

"It's one of the things we do." Serafall confirmed. "But the real reason is because Devil society nearly wiped itself out from centuries of war. And before you ask, no, we do not reproduce at the same rate as humans do. We're usually only able to have children of our own once every few years. So to deal with that, we came up with a little system of our own known as the 'Evil Piece' system."

"And it was Evil Pieces that you put in me and Illya?" I asked, already suspecting the answer.

"Correct!" Serafall exclaimed. "Now both you and your little nee-chan are Devils!"

"Wait a second." I said. "I only agreed to give you my soul—not Illya's!"

"Easy there." The Devil girl said as she pointed her wand at my face. "No need to fret, I'm upholding my end of the bargain. That is why only you are going to be a part of my Peerage and little Illya gets a free ride to a new home."

"Peerage?" I repeated in question. "What's a 'Peerage' supposed to be?"

"Allow me to continue my little explanation from earlier." Serafall replied. "The Evil Piece system was designed as a way to bolster our ranks against threats in a shorter amount of time than replacing them the old-fashioned way. It is been in place for the last two centuries, which means it is still somewhat new to us Pure-Blooded Devils who live for centuries to even a millennia."

"You make it sound like you don't even know how long you live." I pointed out.

"There is a reason for that." She replied. "No Devil on record, Pure-Blooded or otherwise, has ever managed to live out their full lifespan. See previous explanation on centuries of war."

"So you clearly still get into battles." I surmised. "So a 'Peerage' is like a team or a unit that helps you fight?"

"In simple terms, yes." Serafall answered. "Peerages and the Evil Piece system are both inspired from chess. The total number of people in a Peerage can reach as high as sixteen, assuming that everyone gets a single Evil Piece. It is also those pieces that determine one's role in a Peerage. For example, Rooks are typically stronger or at least more durable than, say, a Pawn. Knights, on the other hand, are often fast, skilled warriors who specialize in close combat."

"I get how that would make things easier to organize." I said. "But you also said 'assuming' everyone gets a single Evil Piece. Can a person have more than one?"

"Indeed they can." the Maou affirmed. "Most often, a person is given more than one Pawn piece, though there are cases where a Bishop is given both Bishop pieces or a Rook is given both Rook pieces. Obviously, you can't mix and match pieces as that tends to have some messy results."

"But there would still only be one King and one Queen piece." I thought aloud before realization suddenly hit me. "And the piece you gave me was a Queen piece!"

"Thaaaaaat's riiiiiiiiight!" Serafall cheered happily as she pointed her wand at me again. "Starting today you, Emiya Shirou, are to be the Queen of my Peerage!"

"But, you know, it's just..." I fumbled with my words, trying to think of what I could say. "I'm a guy."

"Oh, don't worry about a little detail like that." She replied with a wink. "I'm a 'King', after all, even though I'm a girl. The important thing is that you know what your role in my Peerage is."

"What does a 'Queen' do in a Peerage?" I asked, but for some reason partially dreading the answer.

"Basically, you will be my right hand." Serafall answered. "You will be my 'guard dog' when I need you, my 'errand boy' when necessary, and, more often than you will initially realize, a representative for me. You will also need to fill a couple other roles, given that we're a bit short-handed."

"How short-handed are we, exactly?" I asked, dreading the answer again.

"As of today," she replied before holding up two fingers, "This Peerage has exactly two members! You and me!"

"You mean…we're all there is." I said while pointing at myself and then her. "Us against who knows how many complete Peerages?"

"Oh relax." Serafall said dismissively. "I didn't bring you into my Peerage on a whim. You, Emiya Shirou, are strong. You have stood your ground against beings who could wipe out armies with what little you had, and managed to come out on top, or at least escape. But that was in your world, where the limits on magic are much higher. Here, though, magic flows much more freely and can be wielded much more easily."

"Magic…flows more easily here…" I repeated before deciding to test it myself.

I held out my right hand, and took a breath as I prepared to use my magic. The familiar image of a revolver cocking entered my mind as I activated my Magic Circuits. And then, I spoke the words:

"Trace. On."

In hardly a second, the outline of my chosen weapon materialized on my hand: It was Archer's white blade.

"No way." I said as I examined the sword, noting that not only had it been produced without hardly a strain on my body at all, but also the usual flaws that would be found in one of my projections were nowhere to be seen.

I had created a perfect replica.

To ensure that it wasn't some sort of fluke, I dismissed the blade and summoned another—one of the blades I had used against Gilgamesh.

Again, it appeared with seemingly little effort on my part, and it was just as flawless as the first reproduction. I did it again and again as a feeling of elation grew within me.

I could use it. I could actually use Unlimited Blade Works to an extent that I wouldn't have even dreamed was possible.

"I see that you're starting to come around on our little deal, Shi-chan." Serafall said with a playful smile. "Obviously, we've still got a lot of work to do, but we're not as behind as you might think. Once you get a handle on your abilities, I'm going to reveal you to the Underworld and then, the sky's the limit!"

I didn't know it at the time, but this was the moment my life would take bizarre turn after bizarre turn.

But the oddest of all would be when I, the Demon Lord's Hero, would come face-to-face with a soul who also came from another world. And to say that he had no idea how to feel about it, was an understatement.

And there we have it, the, admittedly short, introduction to the first of our two protagonists! Now we need to ask the question of who is showing up in who's world and how? But naturally we'll need to wait 'til the next chapter, so in the meantime feel free to leave a comment or review about what you liked/disliked or if you've got any neat ideas for future chapters. Be sure to stop in next time as we meet our second protagonist! 'Til then.