Serafall Leviathan and her Queen*
When I sold my soul to the Devil, I thought I was prepared for anything. I wasn't. I didn't expect him to be a her. Or dressed up as a magical girl carrying a pink wand tipped with a cheerful yellow star. Her being a prankster however didn't come as much of a surprise. You know, the Bible would have been a whole lot more interesting if they included stuff like this.
— Shirou Emiya, story summary
A Demon Lord's Hero
is a crossover fic between Fate/stay night and High School D×D, by Fahad09.
Taking from the Fate!Route, Illya dies, and Shirou performs a demon-summoning ritual in the hopes of bringing her back. A girl dressed in pink appears before him and offers to grant his request in exchange for his immortal soul. He agrees without hesitation, much to the girl's surprise and amusement.
Several months later, Serafall Leviathan instructs her new Queen (yes, Queen!), Shirou Emiya, to enroll at Kuoh Academy in order to keep an eye on her precious little sister, Sona Sitri, much to the latter's annoyance.
It currently stands at 26 chaptersnote but appears to be dead after not having been updated since 2020.
This fanfic contains examples of:
- Adaptational Personality Change: Since Asia Argento is a member of Shirou's peerage instead of Rias's, she's less of a Shrinking Violet and more of a hard-drinking goofball.
- Adapted Out: Asia's familiar, a baby lightning dragon named Rassei, is replaced by a terrifying nine-headed Hydra, whom Asia christens Miss Peanut Wigglebutt.
- Affably Evil: Rias is A Mother to Her Men and a Benevolent Boss who always keeps her word, but she also sees no problem letting Issei die at the hands of a Fallen Angel so she can resurrect him as a devil and recruit him into her peerage, which she only does under the greedy belief that he has a supremely powerful Sacred Gear. She also doesn't hesitate to blackmail Shirou in order to prevent him from interfering with this plan. She sees absolutely nothing wrong with any of this, as that's just part of being a devil, as far as she's concerned.
- Affectionate Gesture to the Head:
- Illya, according to Shirou, likes receiving these, and gets pouty when she thinks he's not patting her head often enough.
- Shirou tries to pat Koneko's head during their first meeting. Due to her distaste for physical contact born from an abusive childhood, she quickly backs away before he can and nearly runs off.
- Koneko does this to Shirou while riding on his shoulders in Chapter 13, though it's more mocking than affectionate—or maybe it's both? It later becomes possessive when he tells her that she needs to get off, which she petulantly refuses to do until he bribes her with food.
- The Alcoholic: Asia likes to drink. Since she's barely old enough to attend high school, she gets drunk rather easily.
- All There in the Manual: Several chapters are excerpts of in-universe documents, and serve to provide setting information.
- An Ice Person: Serafall's powers are ice-based.
- Beware the Silly Ones: Serafall is one of the goofiest beings you'll ever meet, but she is the Queen of Hell, and when sufficiently provoked, she is absolutely terrifying.
- Big Brother Instinct: Shirou sold his soul to bring Illya back to life, and would do even more than that to keep her safe.
- He also develops an obsession with helping Koneko conquer her inner demons so she can become more expressive.
- Big Sister Bully: Karasuba hates Issei, calling him "worm" and treating him with contempt.
- Big Eater: Koneko is a bottomless pit. Shirou even notes that, without Serafall providing him with limitless funds, the little nekomata would have eaten him out of house and home long ago.
- Blood Knight: Karasuba lives for violence.
- Book Dumb: Subverted. Shirou isn't especially studious, but he maintains a respectable GPA.
- Born Lucky: Subverted. Rias and Sona think the former is this due to her getting such an effective Peerage. It turns out that Sirzechs secretly arranged for her to acquire them, in order to give the rest of the Underworld the impression that she has the Power of Prophecy.
- Devils as a whole either have this or Born Unlucky, depending on your perspective. Basically, they have a racial ability called "Luck of the Devil"; which can even rival the luck of dragons at high enough levels, attracting other powerful beings, potential mates of the opposite sex, and leads them to stumble into rather odd situations, like running into a Damsel in Distress on the way home from work or a Virgin Sacrifice on a late-night stroll (all four Satans have experienced both scenarios, Asmodeus even deliberately avoids trying to become a Super Devil because he fears what would happen with his luck if he did).
- Cat Girl: Koneko. When she samples Shirou's cooking for the first time, he imagines a pair of cat ears appearing at the top of her head and shooting up in surprise. She eventually becomes comfortable enough around him to show off her ears and tail in his presence.
- Cats Are Mean: And according to Koneko, they're cute enough to always get away with it, nya-ha-ha!
- Cerebus Syndrome: "All Know Its Name" is an entirely serious chapter, with no funny moments whatsoever.
- Chess Motif: Sona, due to her love of chess, models her peerage off of a chess set. Shirou bluntly explains why this is actually a bad idea.
- Clingy Jealous Girl: Koneko and Illya can't stand one another, as both of them compete viciously for the title of "Shirou's cute, white-haired little sister". The fact that Illya hates cats (and Koneko is a Cat Girl) doesn't help.
- Cool Big Sis: Serafall towards Illya.
- Crippling Overspecialization: Kiba prefers using European swords. Shirou tries to (literally) beat that focus out of him.
- Cute Kitten: Koneko is an adorable little ball of fluff, who happens to be a cat demon. Her name even means "kitten" (or, if you want to be literal, "child cat").
- Cuteness Equals Forgiveness: Koneko is so adorable that Shirou can't bring himself to get mad at her for stealing his lunch.
- Cuteness Proximity: Due to Serafall's influence, Shirou can't resist thinking about how cute Sona is.
- Deconstruction Crossover: A number of standard DxD cliches are torn down.
- The author utterly loathes the Fandom-Specific Plot of a total badass getting easily killed by Raynare and turned into a Pawn piece. Thus, Shirou is made Serafall's Queen piece, which the author feels is more fitting (and funny).
- Shirou cuts the series' Chess Motif down to size by explaining how a real battle is absolutely nothing like a chess match: no two combatants are the same; weather, terrain, and equipment need to be considered; and chess always begins with both sides having equal forces, whereas no real battle would ever have such a thing.
- The different values between humans and devils is shown in a much more sinister light, especially regarding Rias: her decision to let Issei be killed by Raynare so she can recruit him into her peerage is seen from Shirou's point-of-view, so it comes off as incredibly selfish and narcissistic; and while she is determined not to marry Riser Phoenix, she's also too greedy and power-hungry to give up her position as the Gremory heiress. In the latter case, when Shirou asks why she doesn't just do that, Serafall and Ajuka look at him as though he's crazy.
- Defrosting Ice Queen: While Koneko is never outright mean to Shirou, she maintains her emotionless demeanor around him. Eventually, he breaks through it and she becomes a cheerful, mischievous little girl when they're in private.
- Demoted to Extra: Issei doesn't get much focus.
- Education Boss: For all her goofiness, Serafall takes education very seriously, which is why she teased Shirou about being a high school dropout until he agrees to go back and complete his studies.
- Dumb Blonde: Kiba is regarded as this by Shirou, with the latter calling the former the greatest idiot he has ever known behind his back.
- Eldritch Abomination: Sirzechs' true form is so terrifying that it caused Shirou to develop a burning hatred for him. Serafall's true appearance is one, as well, and she is terrified of letting Shirou see it.
- Even Evil Has Loved Ones: Karasuba deeply loves her parents, and trying to harm them will bring her wrath down upon you.
- Failed a Spot Check: When Family Day rolls around, Sona and Rias take drastic measures to ensure their respective older siblings don't show up and publicly embarrass them, mainly by deceiving them into thinking that the gathering will be taking place a week later. Unfortunately, neither of them bothered to tell Shirou about this, and he proceeds to wreck their plans by simply calling Serafall the night before the event to clarify that she and Illya will be coming, which results in them realizing that she was given the wrong date.
- Food as Bribe: Shirou describes this trope as the best way to deal with stubborn and possessive white-haired little girls.
- Hair-Trigger Temper: Downplayed, but acknowledged. Shirou's natural sin is Wrath, which means that pushing any of his buttons will result in him unleashing a storm of swords upon anyone stupid enough to do it. Just thinking about things that piss him off—such as Koneko's backstory and threatening Sona—can cause him to unconsciously commit acts of violence.
- Hates Being Touched: Due to her Dark and Troubled Past, Koneko nearly bolts after Shirou tries to pat her head.
- The Hedonist: Asia, due to her sheltered upbringing, is obsessed with trying anything new if she thinks it might give her some sort of pleasure. Her personal sin being Greed only strengthens this obsession.
- Holy Burns Evil: Holy weapons are exceptionally deadly to devils. Even saying God's name can cause a devil to suffer headaches. Averted with Shirou whom, despite being a reincarnated devil himself, suffers no ill effects from any of these things.
- Impact Silhouette: Averted. Shirou recalls an occasion in which Serafall tied him up and booted him off a cliff, and after he landed, he noted that the impact point did not resemble him in the slightest.
- Killed Offscreen:
- Raynare and her gang are disposed of in this manner by Kokabiel.
- Valper Galilei and Freed Sellzen are executed by the Church without ever interacting with the protagonists in-story.
- Laughing Mad: Sona laughs insanely after learning that Issei wasn't as powerful as Rias thought he was, and even throws in a victory dance for good measure. She does it again when she thinks she's prevented her sister from attending Family Day.
- Made of Evil: Or, at least, made of sin. In this story, devils need to have a personal sin just to exist. Chosen ones tend to be preferred over natural ones, as the latter tends to be more difficult to control.
- Meet Cute: Unlike in canon, Kiritsugu told Shirou about Illya before dying, thus when they met for the first time, Shirou hugged his sister and swung her around playfully, much to her surprise.
- Misery Builds Character: Sona develops a (snarky) sense of humor when put under extreme physical stress. Shirou internally notes that if Serafall ever learned this, she'd go Drill Sergeant Nasty on the poor girl's ass—and considers Sona lucky that he isn't cruel enough to tell his mistress.
- Mythology Gag: Illya's character page on the Type Moon wiki says that she doesn't like cats, though this is never brought up in any of the routes. Here, it's one of the reasons why she and Koneko hate each other.
- Noodle Incident: Shirou stumbled upon a Cthulhu ritual—which involved sacrificing children—while searching for the bathroom and thwarted it. The event is mentioned a couple of times, but is never described in detail.
- Not Big Enough for the Two of Us: As far as Illya is concerned, Shirou can have only one stubborn, possessive, adorable, white-haired little sister. This, coupled with her distaste for cats in general, leads her to butting heads with Koneko, who's just as unwilling to share.
- Not So Stoic: Sona tries so hard to be The Stoic, but Shirou and Serafall can break through that demeanor with ease.
- Parental Favoritism: Lord and Lady Sitri dote on Illya, to the point of giving her a bigger allowance than Sona.
- Puppy-Dog Eyes: Koneko and Illya use this trope to get Shirou to do their bidding. It never fails.
- Red Eyes, Take Warning: When sufficiently pissed, Serafall's eyes go from pink to red. And ice begins to form around her.
- Replacement Goldfish: Illya dubs Karasuba Hyodou "Berserker" and treats her as such.
- Roaring Rampage of Revenge: After thwarting a Cthulhu ritual that involved sacrificing children (the first victim was about to get their throat slit when Shirou arrived) and returning them to their homes, Shirou hunted down everyone with even the slightest connection to the incident and gruesomely butchered them.
- Rule of Funny: Serafall likes to invoke this whenever she does something ridiculous. Shirou worries that it's beginning to rub off on him.
- Running Gag:
- Shirou's chosen sin, pride, getting constantly trampled on.
- Koneko appearing whenever Shirou has food or is in the process of cooking a meal.
- Asia getting drunk and then doing something stupid.
- Sona getting embarrassed by Shirou's actions, whether he intended for her to be or not.
- Ship Sinking: Asia has zero interest in Issei, since they never meet.
- Sic 'Em: Illya (literally) dreams of unleashing Berserker on Koneko.Illya: (mumble) Berserker, kill the kitty.
- Smart People Play Chess: Sona is addicted to playing chess.
- Supreme Chef: Shirou's cooking skills are top-notch, and him becoming a Devil enhanced them exponentially.
- Sweet Tooth: Koneko's favorite food is yokan, a traditional Japanese chocolate-style treat.
- Through Her Stomach: A non-romantic example, but Shirou gets Koneko's attention after she samples his cooking.
- Tiny Guy, Huge Girl: Sona and Serafall's parents, Stheno and Liliana Sitri.
- Too Dumb to Live: Riser Phoenix, Rias's fiance, loudly brags in front of the Elder Council—which her brother is one of the leaders of—that he detests her and has no intention of being faithful to her once they get married. Sirzechs seems to take it in stride, but Shirou can tell that he is absolutely furious. He later plans to have Riser killed.
- Training from Hell: Shirou is not a soft-handed combat teacher. Judging from Sona's reaction, Serafall is even worse.
- Troubling Unchildlike Behavior: Shirou regards Koneko's emotionless mask to be this, as he believes that someone so young and cute should be more emotive.
- The Unfought: Valper Galilei is executed for his crimes by the Church before Kiba can exact revenge upon him.
- Unreliable Narrator: Word of God is that Shirou is not always correct in his observations.
- Used to Be a Sweet Kid: Inverted. Serafall used to be a gloomy, humorless girl who spent most of her time burying her nose in a book. Then a witch named Evelyn came along and essentially taught her how to have emotions.
- You Have Failed Me: Kokabiel sent Raynare and co. to protect Issei from being sought out by devils or angels, but they (possibly deliberately) misinterpreted his orders and decided to kill him in order to prevent any faction from utilizing his Sacred Gear—which instead allowed Rias to resurrect him as a devil and make him a member of her Peerage, the very outcome Kokabiel wanted to avoid. He promptly executes the entire gang when he finds out.
- You Remind Me of X: Karasuba reminds Illya of Berserker.
