Fanfic / Fate DxD AU

Fate DxD AU by QuartzScale is a crossover between Fate/Grand Order and High School D×D.

When Chaldea detects another corrupted Holy Grail in a parallel world, Ritsuka Fujimaru and his Servants prepare to Rayshift and retrieve it. Before the trip, his Servant Magical Girl Illyasviel von Einzbern gave him Class Cards of all his Servants, allowing him to temporarily take on their powers. Unfortunately, a malfunction results in Ritsuka being sent to the world of DxD, in Kuoh Town, alone. Unable to contact Chaldea or summon anybody, Ritsuka quickly makes contact with Rias Gremory and temporarily joins her Peerage (though he remains human) to have a base of operations and resources to seek the Grail. Meanwhile, Rizevim Livan Lucifer tries to revive Trihexa, but ends up reviving Goetia, who starts to resurrect its Demon Pillars and seeks to wipe out the DxD world, seeing it as unworthy.

The fic is available on FanFiction.Net here and on Archive of Our Own here. The fanfiction.net page censors the sex scenes, while the AO3 page is uncensored.

---

This story contains the following topes:

• Adaptational Backstory Change: In the video game, Ritsuka was a seeming Mage Born of Muggles who had no idea the supernatural existed until he was recruited into Chaldea. Here, he was from a Magus family, but since both of his parents did not have powers, he was raised as an ordinary boy, but he at least knew the supernatural existed.
• Anti-Regeneration: Ritsuka defeats Riser Phenex by summoning Lobo and having the wolf savagely maul him over and over again until his regeneration is overtaxed.
• Aren't You Going to Ravish Me?: When Ritsuka defeats Yubelluna in a sparring match, she thinks that he will rape her because that is what Riser would do, and gets confused when he does not.
• Bag of Holding: Ritsuka has a device that lets him store a nearly infinite amount of stuff, one of his few personal accomplishments in magecraft.
• Batman Grabs a Gun: Yuuto Kiba normally prides himself on conducting chivalrous and fair one-on-one sword duels. When he duels Karlamine during the Rating Game, he realizes he cannot beat her unless he fights dirty and that victory for Rias' Peerage is more important than his pride. He hits her with a tackle and a kick, which Karlamine complains is cheating because they had been exchanging pure sword strikes, and then uses Sword Birth to skewer her when Ritsuka distracts her.
• Because You Were Nice to Me: When Hades rescues Ritsuka from Demon Pillar Baal, Ritsuka says he is glad to see him. Hades is touched because everybody else was afraid of him for being the God of the Underworld and nobody gave him such kind words before. Hades resolves to protect him.
• Bedmate Reveal: Ritsuka usually sets up a Bounded Field around his room when he sleeps. Whenever he forgets to do this, he usually wakes up to find Rias, Akeno, and/or Asia in his bed. Even when he does do this, Rias can just destroy the Bounded Field with her Power of Destruction and enter his room anyway.
• Best Her to Bed Her:
  • Sona Sitri earlier promised she would only marry a man who could beat her in chess. When Ritsuka beats her, she becomes attracted to him.
  • When Ritsuka defeats Raynare and spares her life, she becomes attracted to him.
• The Bet: When the Rating Game between Rias and Riser Phenex happens, Rias ups the stakes by saying if Rias loses, she'll marry him and her Peerage will become his slaves, but if Rias wins, all of Riser's Peerage will belong to Ritsuka. Out of arrogance, Riser accepts and loses.
• Blade Lock: Ritsuka and Xenovia get into one with their swords Gram and Excalibur Destruction. Since Ritsuka is using the power of Sigurd, he is strong enough to hold Gram with one hand, then he punches her with his free hand to knock her out. All the while Xenovia was shocked because Excalibur Destruction is supposed to destroy anything it hits. Ritsuka explains in his head that he chose Gram because it is conceptually equal to the original Excalibur, so he knew it could block it.
• Boxing Lessons for Superman: When Ritsuka notices how most of the Devils are Unskilled, but Strong, he makes it a point to train them. He teaches Quetzalcoatl's style of Lucha Libre to Koneko, the Jacob's Limbs style of Saint Martha to Asia, Rias and Akeno how to be more creative with their magic, Shuriya the art of knife-throwing, etc.
• Broken Pedestal:
  • Riser's Peerage, especially Yubelluna, are disappointed when he bet their freedom on a Rating Game without even consulting them. They get really turned off when he loses and develops a extreme phobia of dogs.
  • Irina Shidou gets disappointed with her childhood friend Issei when she learns that he became a Fallen Angel to try to get a harem.
• But for Me, It Was Tuesday:
  • Ritsuka has accomplished so much that he doesn't really think of his deeds as special. This includes killing several dragons, which utterly shocks his peers when he proves it by producing a dragon's fang.
  • When Kiba confronts Valper Galilei, the one who put him and other children through the Holy Sword Project that killed many of them, Valper doesn't remember him and doesn't care about the children he killed.
• Butt-Monkey: Every time Issei Hyoudou shows up, he is made a fool of somehow.
• Chick Magnet: As usual, Ritsuka is one. So far, he's attracted Rias, Akeno Himejima, Sona Sitri, Koneko Toujou, Asia Argento, Raynare, Ravel Phenex, and a majority of the Phenex Peerage.
• Crushing Handshake: When Koneko shakes Ritsuka's hand, she deliberately squeezes with her Super-Strength, but he uses Reinforcement Magecraft to match her strength. He comments to himself that his super-strong Servants used to do that to him all the time, so Reinforcing himself has become second nature.
• Curb Stomp Cushion: Ritsuka easily defeats Raynare and her flunkies, but not before Dohnaseek manages to slash him across the torso.
• Demoted to Extra: Issei doesn't join Rias' Peerage and barely appears.
• Didn't Think This Through: Issei eventually joins Azazel and becomes a Fallen Angel, thinking he can get a harem. Even though Azazel explained that Rias and Akeno are Devils, he didn't stop to think that becoming a Fallen Angel will make it harder to get with them.
• Don't Call Me "Sir": Asia keeps calling her savior "Ritsuka-sama", no matter how many times he tells her to drop the honorifics and just call him Ritsuka.
• Dramatic Irony: Ritsuka and Goetia are unaware that the other is around. Goetia declares that since Ritsuka isn't in this world, it cannot be stopped.
  • Sirzechs agrees to move Ravel and the Phenex Peerage into a different home, but gets one on the same block, citing concerns that Diodora, whose feud with Ruval Phenex has become public knowledge, might try to strike at Ravel in a rash attempt to avenge his recent humiliations. He actually is planing a rash attack for that purpose, but on Asia.
• Evil Is Not a Toy: Shortly after being resurrected, Goetia tortures and kills Rizevim.
• Experienced Protagonist: Having been fighting to save the world for five years and extensively trained by his Servants, Ritsuka is quite skilled and experienced in many fields.
• Eye Color Change: Whenever Ritsuka Installs a Class Card, his eyes change to match the Servant he is emulating.
• The Force Is Strong with This One:
  • Koneko and a few other characters can sense Ritsuka's power. She describes it as wild.
  • As soon as Ritsuka enters the Occult Research Club, he detects Gasper Vladi. When Rias explains that he is shy and refuses to come out, he accepts it.
• For Want Of A Nail:
  • Goetia kills Rizevim, putting an end to his schemes.
  • When Ritsuka joins Kuoh Academy, Raynare senses his power, thinking he has a Sacred Gear, and asks him on the date instead of Issei. When she reveals her true form and attacks him, he easily beats her and her flunkies, then Azazel punishes them. As a result, Issei does not become aware of the supernatural until later, and does not join Rias' Peerage.
  • Since Raynare was taken out, Asia Argento arrives in Kuoh without any problems. Freed Sellzen tries to attack her alone, but Ritsuka easily fends him off and takes her to Rias. Asia still becomes a Devil, but because she chooses to, not to save her life.
  • Azazel later contacts Issei and recruits him, resulting in him becoming a Fallen Angel instead of a Devil.
• Flynning: Yuuto Kiba is normally a skilled and disciplined swordsman, but holy swords are his Berserk Button. Whenever he fights someone wielding a holy sword, he goes berserk and attacks the sword over and over again, even though his summoned swords always break against them, causing him to lose. Ritsuka points out that swordplay is about attacking the opponent's body, so Kiba could have won if he just bypassed the holy sword and stabbed the wielder, but he can't get over his hatred and keeps doing this in later fights. Realizing Kiba won't change anytime soon, Ritsuka provides him with Black Keys, which are durable enough to stand up to holy swords to give him a chance at survival.
• Freudian Excuse Is No Excuse: When Ritsuka learns why holy swords are Kiba's Berserk Button (he and several other children were subjected to dangerous experiments involving holy swords that resulted in many of their deaths), he is not impressed. Ritsuka says that while what happened to him sucks, that is no excuse for Kiba going crazy whenever he sees a holy sword and endangering both himself and his comrades in his mad attempts to destroy the nigh-indestructible weapons. Ritsuka also calls him out on his Misplaced Retribution, pointing out that since the holy swords are not sentient, he should strive to find and punish the ones responsible for the experiments.
• Freudian Threat: Issei mentions that Raynare threatened to castrate him to make him stop hitting on her.
• Heroic RRoD: The Class Cards use up a lot of Mana, so if Ritsuka uses them for too long or if he tries to use more than six in a row, he'll collapse in exhaustion and pain and his body overheats. Fortunately, he usually has Asia on hand to heal him.
• Human Resources: Goetia and the Demon Pillars are murdering Devils to use their flesh to summon more Demon Pillars.
• Humiliation Conga: Diodora suffers this due to a failed attempt to use the Gremory-Phenex Ratings Game to get Asia. He leaks information about Ritsuka to Ruval, which leads to escalating the stakes of the Ratings Game. When it ends up as a Curb-Stomp Battle in the Gremory Peerage's favor thanks to Ritsuka, Ruval takes it out on Diodora. He then spends the next several days hiding from Ruval, and by the time the dust settles, Kokabiel has fallen, eliminating his contact with the rogue Fallen Angels, his family replaces him with his sister as head of the Astaroth family, and the rest of the Khaos Brigade cuts him off as a liability. Driven to the brink, he decides to directly attack Asia in a desperate attempt to salvage his pride...only for Ritsuka to intercept him.
• I Can't Sense Their Presence:
  • When Ritsuka sets up a Bounded Field, no one can sense what happens inside.
  • Raynare pretends to be the human Yuuma Amano by using a spell to conceal her energy signature. However, it ends up working too well, to where Ritsuka can't sense anything from her, even a normal human's energies. This immediately makes him suspicious, allowing him to see her attack coming.
  • Whenever Ritsuka Installs an Assassin Class Card and uses Presence Concealment, no one can detect him.
• I Gave My Word:
  • Shortly before the Rating Game, Ritsuka promises that he will take out at least half of Riser's Peerage with his first attack. He does as he promised.
  • When Rias wins the Rating Game, Lord Phenex, Ruval, and Riser are really reluctant to honor the wager, but Lady Phenex points out Devils must always honor their deals and delivers Riser's Peerage to Ritsuka herself.
• I Know You're Watching Me: Rias questions Ritsuka while her Peerage, Sirzechs, and Grayfia are behind a one-way mirror. During the conversation, Ritsuka suddenly turns directly to Sirzechs and makes it clear he knows he is there, scaring Sirzechs.
• I'm Not a Hero, I'm...: Ritsuka doesn't see himself as a hero, just a guy struggling to survive.
• Literal-Minded: Asia is sheltered so she does not get figures of speech. When Ritsuka says she should take whatever Aika Kiryu says with a grain of salt, she starts looking for salt. When he says his heart cannot take her cuteness, she thinks he is having a heart attack.
• Living Lie Detector: It is mentioned that gods can instantly detect if a mortal lies to them.
• Long List: Ritsuka lists the women in Chaldea in love with him besides Mash.
  "Nero Bride, Jeanne Alter (both versions), Artoria Alter (all three versions), Kiyohime (both versions), Minamoto no Raikou (both versions), Ushiwakamaru (all three though Avenger was reluctant), Tamamo Cat, Mata Hari, Carmilla (both versions), Tamamo no Mae (Shark mostly), Anne Bonney and Mary Read (already considered him part of their union) , Serenity, Gorgon (reluctantly), Musashi (Berserker mostly), Meltryllis (both versions), Passionlip, Schercherazade, Osakabehime (both versions), Circe, Ereshikigal, Okita Alter, Scathach Skadi (in the most tsundere-ish way possible), Qin Liangyu, Kingprotea, Kama, Sima Yi (Reines, the host expressed interest), Murasaki Shikibu (both versions, though Caster more so), Okita Souji (Assassin was more open), Lancer Artoria, Caster Artoria, Morgan, Barghest, Baobhan Sith (In a weird twisted way due to kindness), Melusine… a lot of women had wanted dibs on him. What made it worse was that with how naive Mash was sometimes she had let slip she would share."
• Mugging the Monster: Shortly after Ritsuka arrives, some thugs try to mug him, but he easily beats them up. Raynare and Freed Sellzen similarly underestimate him.
• Mundane Luxury: Since Ritsuka had been fighting to save the world out of a base in Antarctica and then the Shadow Border for about five years, he is giddy just to be able to roam around a town and then go to school.
• Mundane Utility:
  • When Ritsuka plays chess against Sona, he cheats by using Sha Naqba Imuru (from Kid Gil's card) to predict Sona's moves and thus win easily.
  • Ritsuka stores food in his Bag of Holding. Not only does this make it easier to carry, but time is also frozen within, so it won't become cold or spoil.
• Nested Ownership: Ritsuka is technically subordinate to Rias. Ravel, the new King of Riser's Peerage, is subordinate to him, and her Peerage to her.
• Never Gets Drunk: Ritsuka's contract with Mash renders him immune to all poisons, including alcohol. Zeoticus Gremory and Ruval Phenex try to get him drunk so that he'll spill his secrets; instead, Ritsuka drinks both of them under the table. They're even a bit embarassed over how poor their own showing was, by comparison.
• Newspaper Dating: Ritsuka finds a newspaper that says it is 2008. In his own world, it was about 2021.
• Nice Job Fixing It, Villain: Baal's obsession with killing Ritsuka, to the point that he even manifests as an Avenger-class, is likely going to clue him into Goetia's survival/resurrection.
  • Ritsuka only gets the opportunity to inform Azazel, and through Azazel Serafell, about Goetia because Baal tried to kill Ritsuka in their sleep.
• Normal Fish in a Tiny Pond: Ritsuka constantly thinks of himself as a weakling and amateur. This is because the only people he had to compare himself to are Servants, who are vastly superior to humans. In the DxD world, even without the Class Cards he is quite formidable.
• No-Sell: Ritsuka uses Medea's card to produce Medea's potion that renders the drinker fireproof. He drinks one and gives the rest to Rias' Peerage, making Riser's Peerage unable to harm them with fire attacks.
• Not Afraid to Die: Ritsuka isn't afraid to die, which means he won't hesitate to do stunts like jumping out of the sky to tackle an opponent. His Servants have repeatedly confronted him over this and say his recklessness may get him killed, but he refuses to stop out of a need to prove himself useful.
• Not Me This Time: While investigating the various Devil murders caused by Goetia and the Demon Pillars, The Four Great Satans and other authorities assume at first that they were caused by the Old Satan Faction. Then they realized they didn't do it because many of the victims are pure-blood Devils.
• Not Worth Killing: When the Demon Pillar Flauros meets Diodora, he considers Diodora to be so pathetic that killing him would be a waste of energy.
• O.O.C. Is Serious Business: In a flashback, Assassin EMIYA actually dropped his usual stoic demeanor in order to warn Ritsuka about Alaya and beg him to never accept a deal to become a Counter Guardian.
• Oh, Crap!: When Ritsuka reveals Goetia's existence to Azazel, he nervously calls up Serafell asking if she's seen any devils that shouldn't be there. During this time, he's seen having gone through at least 4 drinks.
  • Downplayed and eventually subverted with Serafell who reacts appropriately when she gets the same information Ritsuka gave Azazel. Shortly after, she calms down, and notes this is an opportunity to squeeze more information out of Ritsuka via Sona.
• Older Than They Look: Ritsuka joined Chaldea when he was sixteen and has been fighting the Singularities and Lostbelts for five years, making him 21. He looks like he's about seventeen, so he gets enrolled in Kuoh Academy.
• One-Steve Limit: Averted. The various factions try to look up Ritsuka to learn more about him. In the DxD world, there are about 20 Ritsuka Fujimarus, and none of them are him.
• Polyamory: Mash is still a Clingy Jealous Girl, but realizing that she'll never be rid of Ritsuka's harem, gave him permission to be in multiple relationships, so long as she remains Number One. Rias and Akeno eventually persuade him to enter relationships with them as well.
• Pretender Diss: Goetia and the Demon Pillars dismiss the Devils as inferior to Demons.
• Rain of Arrows: As soon as the Rating Game begins, Ritsuka uses Atalanta's card to unleash her Noble Phantasm, Phoebus Catastrophe, firing two arrows that turn into this. Riser's Peerage tries to stop them with fire spells, but since these are energy arrows, they pass right through the fire and take out all eight Pawns, one Knight, one Bishop, and one Rook.
• Rank Up: When Ritsuka gets control of Riser's Peerage, Lady Phenex attempts to turn him into a King with the Evil Pieces. Ritsuka, who is adamant about remaining human, tells her to use it on Ravel, turning her from a Bishop to a King.
• Save the Villain:
  • Shortly after Raynare and her flunkies are defeated, Azazel prepares to execute them for violating his orders. Ritsuka persuades him not to, so Azazel demotes them into his personal servants.
  • When Kokabiel attempts to kill Valper Galilei, Ritsuka saves him because he knows Kiba will never get closure unless he confronts him.
• Secret-Keeper: Ritsuka eventually tells Rias' Peerage about how he is from another world and about Chaldea. When he gets control of Riser's Peerage, he decides to wait until they are ready to tell them.
• Sex God: Ritsuka is extremely experienced in bed, due to having to keep up with the superhuman Servants he sleeps with, most especially Jeanne and Artoria Alter. When he sleeps with Rias and Akeno, he lasts so long that they pass out from exhaustion. As he puts it, he's a marathoner, not a sprinter.
• Shipper on Deck:
  • Sona Sitri's Peerage supports her and Ritsuka, much to her embarrassment.
  • Lady Phenex supports Ravel and Ritsuka, since she sees that he's strong enough to protect her.
• Stepford Smiler: Ritsuka really misses his parents and school friends from before he joined Chaldea. Now that he's stranded in the DxD world, he really misses Mash Kyrielight, his other Servants, and the Chaldea staff and laments that he can't contact them. He hides his pain from everyone.
• Summon Magic: Though Ritsuka cannot summon any Servants, he can summon their mounts, as shown when he uses Hessian's card and summons Lobo.
• Supernatural Fear Inducer: Because Ritsuka killed Goetia and several Demon Pillars, he is at his core a demon slayer. As Devils in the DxD world are descended from demons, making eye-contact with him causes them to experience a great fear of death. This also happens to other beings like Fallen Angels and humans, though not as intensely.
• The Talk: Aika Kiryu teaches Asia about sex, causing her to want to sleep with Ritsuka.
• This Cannot Be!:
  • Raynare and her flunkies do this when Ritsuka effortlessly beats them up and chops off Dohnaseek's wings.
  • Riser and his Peerage do this when Ritsuka and Rias' Peerage prove fireproof and then they get curb-stomped.
  • Xenovia does this when Ritsuka blocks Excalibur Destruction, which is supposed to be able to destroy anything it touches, with Sigurd's sword Gram.
  • Kokabiel does this when the heroes are strong enough to hurt him and when Ritsuka brings out Prototype Arthur's Excalibur.
• Thou Shalt Not Kill: Ritsuka really tries to avoid killing, though he understands that it is at times unavoidable.
• Trapped in Another World: Ritsuka is stuck in the DxD world.
• Underestimating Badassery: Several characters such as Raynare, Riser, and Diodora underestimate Ritsuka simply because he is a human, only for him to show how powerful he really is.
• Unknown Rival:
  • Issei becomes obsessed with defeating Ritsuka due to Ritsuka having a harem. Ritsuka mostly ignores him, and when Issei tries to attack him, he kicks Issei's ass.
    • As of Chapter 35, Issei and Ritsuka have reached some form of understanding, and thus Issei appears to no longer hate Ritsuka.
  • Freed becomes obsessed with killing Ritsuka due to Ritsuka stopping him from abducting Asia. Ritsuka has trouble remembering his name and kicks his ass whenever they fight.
  • Diodora is obsessed with killing Ritsuka for saving Asia and winning her affections. Since he's hiding in the shadows, Ritsuka doesn't even know he exists.
• Wham Episode: Chapter 33. Edmond Dantes manages to contact Ritsuka in his dreams, letting him know about the time differential, though Dantes is unable to locate him physically. Ritsuka then meets Void Shiki, who reveals that the Counter Force made her send him to the DxD world because Alaya wants him to strengthen the Human Order there, but to balance the equation, Gaia revived Goetia.
• Why Did It Have to Be Snakes?: Ritsuka defeats Riser with Lobo, leaving him with such a fear of dogs that he cowers when he sees a dog plushie.
• Will Not Tell a Lie: Ritsuka made a vow to never lie ever since Kiyohime, whose biggest Berserk Button is lying, joined his harem. He is still able to pull half-truths and Exact Words.
• Wooden Katanas Are Even Better: With the help of Reinforcement Magecraft, Ritsuka can slice a tree in half with a wooden sword, though the sword breaks afterwards.
• Wrong Context Magic: Everyone is baffled by Ritsuka's abilities, especially when he uses the Class Cards, because they are different from Sacred Gears or any kind of magic they are familiar with. When he calls on Lobo, they comment no human can control a wraith, so what they are seeing is unprecedented. When he uses Medea's card, they are shocked that he can fly without wings.
• Year Inside, Hour Outside: For each day that passes in the DxD world, only a minute passes in Chaldea.
• You Have GOT to Be Kidding Me!:
  • Azazel is trying to help Issei rise to greatness, but gets exasperated by his one-track Harem Seeker mind.
  • Ritsuka is in disbelief when he learns that the DxD Excalibur was broken and forged into seven swords, since the Excalibur he is familiar with is the literal embodiment of a concept and thus indestructible.
• You Remind Me of X:
  • Koneko reminds Ritsuka of Asha from the Indian Lostbelt because of her loneliness. She also reminds him of Mash, especially when she calls him "Senpai".
  • Kiba reminds Ritsuka of Gawain, Mordred, and Lobo because he tries to be chivalrous, but he holds great anger inside. He also reminds him of EMIYA because of his Sword Birth ability.
  • Akeno's sex-crazed and sadistic attitude reminds Ritsuka of Artoria Alter, Jeanne Alter, BB, and Queen Medb. Her loneliness reminds him of Lakshmi Bai and Yu Miaoyi.
  • Freed reminds Ritsuka of Rasputin/Kirei Kotomine.
  • Riser's smug attitude reminds Ritsuka of Lev Lainur Flauros.
  • Issei reminds Ritsuka of Fergus because of his sex-crazed attitude.
  • Asia reminds Ritsuka of Mash because of her innocence.
• Your Magic's No Good Here: Downplayed. Most forms of Nasuverse magecraft work in the DxD world, but the spell for summoning Servants doesn't, because the Throne of Heroes doesn't exist there.

---