(Warning: I am bad at writing. I also based anything from the wikia and the TV Tropes, so information for certain thing is quite scarce. Think of this story as a total AU. Also, this story isn't meant for a serious storytelling. Please keep those in mind before approaching the keyboard.)
The shadows… they are up ahead, waiting to slay any living, breathing creatures.
With a team of three of the greatest heroes for mankind, the hero marches forward, ready to engage in an epic battle, specifically to win the fight.
Xxxxxxxxxxxxxxxxxxxx
But that's not what the real hero of the story does at this very moment.
The real hero of this story does none other than staying inside a school of Kuoh Academy, going through classes.
But he does not care about that.
He only cares to watch closely toward the outside of the class.
The man mutters, "This is all your fault, Ritsuka-senpai…"
Xxxxxxxxxxxxxxxxxxxx
[FLASHBACK]
This is indeed the fault of his Ritsuka-senpai.
The black-haired man just sits in the lounge of Chaldea, looking toward the TV screen as it is showcasing an epic fight of an epic proportion.
The red-headed girl besides him is looking excited while leaning forward, seeing how three humans are fighting against a huge non-human creature without being scratched not even once.
She turns toward him, "Look at that, Gudao! Our senpai is so cool with his team of Saber, Archer and Assassin!"
"Yes, Gudako… I get that…"
The girl looks at him, looking confused as she pulls himself up and faces him, "What's wrong?"
"It's Ritsuka-senpai. He said I am too inexperienced to fight on the battlefield."
"He's correct. We haven't been fighting outside of the simulation room at all."
"Yeah, well, how are we going to get experience if the only fight we go to is inside that simulation room?"
"We still need more training if we want to catch up to senpai's level."
"That simulation room is busted because of the fire! We can't do any more training!"
"Just listen to what senpai has to say!"
"He didn't say anything!"
"Guys, what is the problem here? Why are you two siblings fighting?"
"EEEEEKK!"
The two is startled by the sudden appearance of an old man in beard as he grinning at them, "Poor Ritsuka-senpai had to deal with you two…"
At that very moment, a blue-haired man in blue tight clothing comes walking into the lounge as he is freaked out by the sight of the old man, "Shit, it's Zelretch!"
The man turns to see him, giving him a wide smile, "Ooh! Cu Chulainn, how are you today?"
"Get away from me, you monster!"
"You hurt my feeling, you know that? We have been friends for quite some time…" the old man looks pained by his words.
But the man in spandex did not give any shit for that, "Friends do not put other friends into dangerous spots!"
Gudao and Gudako is in shock, seeing the old man as she whimpers in fear, "Y-you meant to say that… he is… he is… that troll vampire, THAT Zelretch!?"
Zelretch glares at them before turning toward Cu, "Oi, what have you told to these pure and innocent children?"
"I'm not the only one, old man! Everybody here knows what kind of person you are; A BIG TROLLING VAMPIRE!"
"You are so family unfriendly, Cu…"
He then turns toward the two siblings, ignoring the man behind him, "You two, I'm bored. Let's go for an adventure."
And at that moment, Gudao Tomiya curses on his senpai for not bringing him into the battlefield.
Xxxxxxxxxxxxxxx
[PRESENT DAY]
Thus, this is how both Tomiya siblings ended up in this strange world.
This world is different than the world they came from. In this world, it seems the Age of Gods is still around.
"Listen. In this place, there is such thing as hell and heaven. Angels live in heaven. Devils live in hell. Fallen Angels stays on earth. There are also other deities from other mythologies."
But why would that asshole even decided to send them here? This is too much for them to handle!
Is there anything for them to do here? Is there something they need to d-
"GUDAO!"
He is quickly taken aback from the scream, turning toward Gudako who is leaning close to him, clearly screaming near his ear.
"Are you daydreaming!?"
"N-no… why do you call me like that?"
Gudako answers him, "I am asking for you to have a lunch with me."
"I… I forgot to bring my bentou…" he quickly looks away, embarrassed of his statement.
Gudako sighs, pulling out two boxes tied together with a cloth, "I have yours. Mou, you always forgot to bring yours…"
Xxxxxxxxxxxxxxx
The siblings are now eating their lunch outside near a bench, silently as they are trying their best to enjoy their foods.
Gudako seems to have her eyes wildly looking all over the place, watching every single moves made by every single person within the Kuoh Academy.
Gudao notices his sister's action and decides to remind her, "Gudako, you are acting so rude right now!"
"Sorry!" she pulls herself, scratching the back of her sheepishly with a wide smile toward him, "It's just so rare to see people living around the place without the need to feel worry of the impending doom of their own world."
"I get it," he mutters as he takes another bite, "Our world has already reached the deadline, so we Chaldea had to initiate Grand Order in order to ensure our survival. That is pretty much what has been ingrained within our heart the moment we decided to sign in into the organization."
She loses her smile, "Ne, Gudao. Do you think Ritsuka-senpai is alright back there?"
"I'm sure he is. He is the Chaldea's top Master after all. He also has several Servants working under him, so of course he is going to be fine."
Gudako moves closer to him after having her head turning around and making sure that nobody is around as of now, "We should summon our own today."
He stares at her for a while, processing his words, "Summon our Servant, you mean?"
She nods excitedly.
Gudao mutters, "We are finally going to do it?"
"Yeah! We need to summon more Servants by our side in case Cu Chulainn needs our help. He alone could not defeat a huge number of enemies. From what he have heard from snooping around before, there are high chances that any of the Three Factions are quite unfriendly toward people like us."
"So, we should at least get some extra protection, is that what you are saying?"
"Of course! This is our chance to prove to senpai how capable we are in the outside world."
As soon as she finishes speaking, a loud commotion is heard coming from the side.
Gudao sighs as he mutters in disappointment, "It's those three again…"
At that moment, three boys are being beaten up with kendo sticks by a large group of girls.
"Again with the peeking!?"
"You guys are really into getting a beating, huh!?"
After much scolds and beats, they promptly leave the area, leaving only the three on the ground, beaten up excessively.
Gudako stares at them for a while before deciding to voice her opinion, "I know I shouldn't be saying this, but those girls from the Kendo Club might have been a sadist. I'm not sure a crime of voyeurism is equal to murder."
Gudao chuckles, "Well, you won't be very forgiving if they saw you in your underwear, right? I'd say they deserve that. It's still a wonder concerning their own resilient to keep on being a peeping tom."
One of the three, the one with a brown hair stood up and screams at him, "Shut up, you damn handsome! You are not the one born with a lovely sister with you! I'm sure she has been waking you up in very suggestive manner every morning!"
"Issei-kun, I suggest that you keep away from porn if you want to have a girlfriend."
He suddenly laughs out loud proudly, "Jokes on you! I already have a girlfriend!"
Gudao now sweating, "Poor girl. I pray for her safety."
"What is that supposed to mean!?"
Xxxxxxxxxxxxxxx
As the scene is played out, a red-headed figure is watching them silently from a building nearby the school's building.
The red-haired female is watching them intently, seemingly analyzing whoever she is focusing her sight on.
She first looks at the loud brunette below them that just stood up from the ground. She then slowly turns toward the twins, the new students that just transferred there few days ago.
A raven-haired female appears beside her, not being noticed the red-headed beauty as she quickly tries to gain her attention, "Ara, ara~. It seems our president have an interest toward someone. Has she finally grown up?"
The "president" is startled by her appearance as she pouts, "Akeno, I've told you before! I was taking a look at our potential recruits."
"You sure take quite a sweet time looking at them, Rias," Akeno teases her.
"Akeno!" Rias pouts again.
She then turns toward a white haired girl sitting near them on a chair. The short-haired girl is silently eating her food as she asks the girl, "Koneko, what did you think about those three?"
She answers with a calm tone, "Hyoudou-senpai has the smell of a dragon with him. But the Tomiya twins have some strange smell on them."
"How strange?"
"I don't know. I have never smelt such thing in my life before. They have too many smells with them, they jumbled up."
"Is it possible for them to have Sacred Gears?"
"Yes."
Rias smiles, "Then, we might as well try our luck with them, that is before Sona gets her chance."
Koneko suddenly has her eyes moving all over the place. She is acting as if a cat is watching over a red pointer being moved around her.
This, of course, gaining Akeno's attention, "Koneko-chan, what are you doing right now?"
She is about to answer, but then her expression slightly changes from curious to confusion as she mutters in her usual tone, "Nothing."
Xxxxxxxxxxxxxxxxx
Cu Chulainn simply walks out of the Kuoh Academy.
That was close.
He was there for the rest of the day, wishing to gain more information but that white-haired girl has nearly caught him being in there.
She must be a special type of devil to be able to even sense him in his spiritual form.
That or his incredibly low luck is playing a sick prank of him.
At least he does get some information from them, though that just brings more questions in mind.
What is a Sacred Gear? What do they want from the twins and a random student? Do they wish to enslave them? Why them?
Cu isn't sure getting into the place back is a great idea. Pretty sure that girl is going to be wary around her for sure.
Man, getting back home is boring. He might as well do something else while waiting for the twins to come back home.
Come to think of it, are those two his masters? Co-masters?
Probably need to ask that question to them later.
Maybe he should go fishing? It's a great way to waste some time.
Yeah, let's do that!
Xxxxxxxxxxxxxxxx
As the school is finally finished, Gudao and Gudako are now walking back home.
Entering the front door of their normal-looking two-floored house, they noticed that someone is already at the living room.
"Owh, no…" Gudao mumbles, knowing exactly who is there right now.
"Welcome home!" Zelretch is sitting on the couch, smiling wide toward the two, "How are your days in the new school? How many friends did you get? Have you been at odds with the teachers? Dating anybody?"
"Shut up," the male student mutters out loud, clearly showing his annoyance toward the old trolling vampire.
Gudako, on the other hand, keeps her optimism up, "Why are you here, Zelretch-san? Is there anything you want to tell us?"
"At least somebody appreciate me being here," the old man glares at Gudao before looking at both of them, "I am here to help you summon your new batch of Servants!"
Gudako quickly responds with, "We're about to do that actually!"
"Really? How?"
Gudao pulls out a notebook, "From what I've learned back in Chaldea, you only need to draw a certain magic circle, put your prana into it while chant certain aria and then you will be able to summon one."
"Boy, if that is pretty much the only think you need to do to summon Servants, the world will have been overrun by one."
"So…" he stares at him, confused.
"What you just described is a way to summon a familiar. Summoning a Heroic Spirit requires a great amount of prana, which is the Masters were given a set of Command Seals. You also need to a catalyst for a certain hero to pop up, or else you might end up with a really weak hero instead. Judging by how low your prana reserves are, that's pretty much the most possible outcome. Not to mention, none of you have a piece of lesser grail, so how are you going to summon one without a connection to the grail itself?"
…
…
…
The twins just stare at him, taking an amount of time before Gudao turning toward his sister, "GUDAKO! I thought you said this is going to work!?"
"Teehee!" she simply scratches the back of her head, grinning playfully.
Zelretch smiles wide, "This is why I'm here! Since you are needed here, I figure why not give you an advantage. Unlike other people I have sent to a version of this world in the past, which is mostly a dude named Shirou Emiya or a bunch of Class Cards for people to use, you guys only have Cu Chulainn by your side, which you guys aren't even contracted to. This story is going to end way too fast if I let you live with that."
Gudao brings up a question, "About the Cu part, how is he still here? He is supposed to be fade away after a few days."
"That, my boy, will be an explanation for the other day."
"You don't actually have an explanation for that, aren't you?" Gudako interrupts.
…
"Anyway," Zelretch slowly turns away from the glaring eyes, "I've used one part of your basement and put the summoning circle down there. The only thing you need to do is to put some of your prana into it and it will give you a random Servant."
"Random!?" Gudao snaps, "Sir, you are the Wizard Marshall himself! No other people with similar title can match you! You, the Kaleidoscope of the True Magic, put us in this strange world and give us a Servant summoning circle BASED ON RANDOM!?"
"It's okay, Gudao," his sister gently pats his back with a reassuring smile on her face, "At least we have a summoning circle."
Zelrect then interrupts, "Owh, by the way. Make sure you put an appropriate amount of prana; not too much and not too little. You don't want to have to explain to the Servants on why did you have way too many Black Keys, right?"
"Black Keys!?" it's Gudako's turn to snap, "Damn you, Kotomine Kirei! Even after death you are still an annoyance to all!"
Xxxxxxxxxxxxxxx
"And that should be the last one for today."
Cu, in his Hawaiian shirt, has finally wrapped up his fishing activity, stretching himself from the long hour of sitting.
He then turns to see the numbers of fishes inside the bucket, smiling at them, "I should release all of you. After all, I only need one of you for dinner tonight."
Wrapping things up, he returns home, following a simple road. The road did not have many people walking there, so he enjoys a calm and serenity time that evening.
When he reaches one place, however, his sight is quickly turned toward a two lovely couple, walking side by side.
"Ah, young love," he mutters to himself, seeing the boy and the girl, clearly students, presumably walking home together, "It makes me wish I were to be born in this era instead."
He is about to move past them and not interrupt them, but had to stop immediately and be alarmed when he head, "Could you please die for me?"
WHAT!?
The girl suddenly has a pair of black bird wings behind her, as she throws a light spear deep into his heart.
"Damn!" Cu runs forward toward him, wanting to save him but he simply falls, looking dead.
He then turns toward her, "Y-you killed him! What kind of student are you!?"
"A witness?" the girl smiles, "I'm sorry mister, but I can't have a witness around here."
She then throws the same spear toward him, but Cu pulls out his iconic red spear and simply deflects it away from him, letting it explodes somewhere else.
"Nice try, Fallen Angel, but after what you did to this poor boy, your chance of escaping is really low. Now tell me, are you after this boy for his… Sacred Gear?"
"Tch!" the girl clicks his tongue, "I see you are well versed in this subject. Are you one of those pagan magicians?"
Cu smirks, "Magicians? If we were in my time, I can be considered as one. But right now I am Lancer, the Spear-Wielding Servant!"
Twirling his spear around, he is ready in his stance with the tip of the spear pointed forward. He is also changes his attire into his blue tight in just a blink of an eye, ready for a battle.
"Servant? Lancer? I have no idea what those terms are referring to, but don't get too cocky, human!"
The girl flies up as she starts throwing more of her light spears. Unfortunately facing against a war veteran like Cu Chulainn, simply throwing some spears ain't gonna cut it, especially since her opponent is a master of his own spear.
He keeps on deflecting the spears away from his own, letting the projectile weapons to be missing their targets.
"You see, I don't really like fighting and killing women, but you can be an exception to me," Cu speaks up as he charges forward.
He suddenly disappears from her eyes, only to see him reappearing beside her and receives a kick that throws her back to the ground.
She tries to throw another spear at him as he lands, but he deflects it one more time and ends his action with an attack right on her stomach with the blunt side of the spear.
As she coughs blood, the pointy side of the spear is pointed close to her, "Tell me good information on anything regarding the Sacred Gears and I'll consider your survival."
For the first time in her life, she felt fear. It could have been originated from how skillful he is, or possibly because the red spear is radiating with bloodlust and looks like it could be a sentient weapon as well.
"Is that spear… a Sacred Gear?"
"Why would you conclude it like that?"
But before she could answer it, he senses an attack and quickly flips forward, landing on his two feet as he sees a light spear nearly hit him, came from behind.
"What is wrong you, Raynare!?" a male Fallen Angel with a fedora on his head appears, screaming at her, "You couldn't defeat a simple human!?"
The girl, Raynare shouts back at him, "Shut up, Dohnaseek! His spear is dangerous!"
"Hurry up then! We will be in deep trouble if the Devils know we are here!"
The Devils? Did he meant the red-headed girl and her club members?
Yeah, he would not want to be caught by them as well. All of those espionages he did before will gone to waste.
He needs to finish up, quick!
Ready in a certain stance of his, he prepares for a stronger attack as the two are now regroup, holding a light spear in each hand.
They are about to approach him, but stop immediately. The spear is now having the smell of bloodlust stronger than usual.
Dohnaseek grins wide, moving forward, "This is going to be fun!"
Fun? Sure, why not?
"GAE… BOLG!"
Cu then throws the spear forward as the spear turns into a red beam and goes toward him.
He quickly flies up as soon as the beam is about to reach him, but an impossible happened.
Or what is expected for a spear bearing such name would do.
The beam somehow changes direction at an quite an impossible angle toward Dohnaseek and forcing him to fly around erratically.
Unfortunately for him, the spear refuses to back down from its chase and keeps on searching after its target; his heart. It is all because the spear runs in the principal of having its target having been pierced, so the spear must have been thrust.
With that in mind, it is clear who the winner here is.
"Arrgghh!" the male Fallen Angel screams in pain with the spear returns back to its owner from his heart. His body collapsed onto the ground.
Raynare turns back toward him, "Th-that's impossible! Gae Bolg? Only Cu Chulainn could use that weapon! A-are you his descendant!? He shouldn't have any left!"
One of the statement pushes his button, "D-Descendant!? Do you really think that a spear that I won from that witch after a grueling torture she called training can be turned into an heirloom for a family of mine!? Fat chance!"
"Y-you!" she grits her teeth in anger and quickly flies away from there.
Cu is about to chase her, but he suddenly remembers something, "The boy!"
He turns back to where the impaled boy fell, but sees nothing there; not even a corpse.
He wanted to feel surprised, but something else forced him otherwise; something that pulls him from there.
Xxxxxxxxxxxxx
"So you only need to press this to call them?"
Right now at the Tomiya household, Gudako is with Zelretch, holding her phone. At the screen of that phone is an app opened, with a picture of Cu and some other blank squares on it.
"Yes!" the old man smiles, "With this, you can call any of your Servants anytime from anywhere. Non-master will found it as a simple incomplete fighting game app, but only you and your brother can use its real function."
"This is convenient! Where did you found this app?"
"Owh, let's just say that in one timeline, Fate/Grand Order is not an RPG game, but a fighting game. Also, in one crossover timeline, the fighting game is actually a Hero Summoning App rather than Demon Summoning App. And in one different timeline, a certain otaku magus that lead an organization made combined both ideas together."
Gudako just stares at him with a smile on her face, clearly froze after being confused by what he told her, but quickly turns back toward her app, "Cu's image blinked before but now it has stopped. Why?"
"The blinking means that he was busy with something; a fight, meeting a potential enemy or simply doing an activity he wishes to not be interrupted. Summoning him at that moment could be a bad decision, but could also save his life from any danger he was facing."
She shrugs, "He's probably gone fishing then. He loves doing that."
He then turns around as he walks toward the door, "Gotta go. I wanted to check this one crossover timeline where I gave this boy who supposed to be a harem king in the future a bunch of cards with Servants in it and inspired him to be a hero instead. I wonder if he even knows how to use those cards. Maybe I should have gave him one of my Kaleidosticks."
That man didn't really use that door. He simply disappears from her sight, leaving her still confused by his words.
Shaking her head, she turns to see the app and presses Cu's face.
At that very moment, Cu Chulainn appears before her, startling him as he looks around the place, "Wh- I'm home? How?"
She explains, "Zelretch gave this app to us! We can summon you or any other Servants anytime we wanted to. Also, you are my Servant now."
"Congratulation?" Cu has no idea if that's a good thing or not. But he quickly remembers something, "No, wait! There is something else you sh-"
"Owh, you're home already," Gudao now appears from the door that leads to the basement, "Good. I can introduce you to my Lancer."
"What?" Cu turns toward him, "Who are yo-"
His eyes widen. His jaw drops. Fear appears inside his body.
Behind Gudao, a purple-haired female wearing a purple tight outfit and leather armor above it appears before the two.
He smiles as he introduces, "Gudako, Cu, Meet Scathach, my Lancer."
Scathach gives off a warm smile at him, "Nice to see you again, Cu Chulainn."
"Y-YOU!? OF ALL PEOPLE, IT HAS TO BE YOU!?" Cu screams with fear overflooding the place.
The witch turns sour looking at him, "I see that your involvement with the Holy Grail War has made you scared of me. Do not worry about that. I may have appeared in the Chaldea for other Master, that is simply a dream of this current me. So whatever I did to you during the Grand Order, it is simply not me."
"Th-th-that's not it! You know what you did to me, you immortal witch!"
"I failed to remember anything I did that would scar you for life," she looks away nonchalantly.
Gudao turns to see him, "Cu, you were gone fishing before, right? Where's the fish? My sister and I can cook something good."
"Ah… the fish…" Cu remembers something, "I… I left it somewhere else…"
Little did he knows, he actually forgot something far more important than a fish in a bucket left on a street.
More important than that, a crow reaches the home, now landing on a tree and watching the house closely, wondering what happened inside the house.
End chapter.
Yes, this story is based on Holding All The Cards by Drow79 and Heroic Straight Flush by L33t Horo. But rather than using the same format of DxD Prisma Illya crossover, I used Dxd F/GO crossover instead.
I had this idea when I read these two lovely masterpieces and hoping for them to update new chapters quickly just to see a possibility of certain scenes play out. But rather than commenting, I decided to make my own take of their stories instead. For those who read those two already will probably realize what may happen next, so there you go!
I'm sorry for the lack of action here. I am bad at fighting scenes and I really wish somebody could help me with that. I may need help for the fight scenes especially…
This story isn't supposed to be a serious story like the two aforementioned stories, but more me being a bored guy doing whatever comes in my mind, so don't expect too much on me.
If you didn't realized already, Gudao and Gudako aren't OCs. They are the protagonists of FGO where the names were given by the fans before the canon name, Ritsuka was given for the upcoming anime.
Also, keeping with what Drow79 and L33t Horo did with their stories, here are the list of known Heroic Spirits:
Gudao's team:
Saber- ?
Lancer- Scathach
Archer- ?
Rider- ?
Caster- ?
Assassin- ?
Berserker- ?
Gudako's team:
Saber- ?
Lancer- Cu Chulainn
Archer- ?
Rider- ?
Caster- ?
Assassin- ?
Berserker- ?
Any suggestions for the team members accepted, though Gudako's Rider and Gudao's Assassin has already been decided.