VotedforKodos

The people who live in Flognarde are naturally subservient and loving to humans. That’s why the three Heroes are so loved and make friends so easily; it’s basically like all the people of Flognarde are pets whose owners came back after being away for a long time. Not a problem for a while, because they were really only concerned with playing games, having fun, and resolving whatever crisis was going on.
 
Then after Double Dash, while they’re at home, some hentai plot happens (doing chores or family beach trip together or whatever) that leads Becky’s mom to seduce Cinque, and Becky to join in when she finds out. After that, it just becomes a regular thing for them to have sex.
 
But when they go back to Flognarde, they separate and can’t, so they get hornier and hornier until their princesses each find them masturbating, and help them along. In Cinque’s case, whenever it happens (which is often, considering the way these girls act around him), he’s helped by whoever is there, regardless of who it is or how public it is.
 
Then it eventually gets explained that it just happens with humans, and that the Hero King went through something similar. Only now, because of the time she spent sealed with the Demon King, she acts the same as the natives of Flognarde, as do Becky and Nanami from using the Demon and Spirit Crystals. So Cinque is, as far as their instincts are concerned, the only pure human in Flognarde.
 
Summary:
Cinque and Becky start having sex when they go home. When they go back to Flognarde, because they can’t regularly have sex with each other, they wind up having sex with other people, who act like standard hentai sex pets. It comes out that it’s normal for people of Flognarde to have that reaction to humans, and Becky, Nanami, and Hero King Adel have, for various reasons, also adopted those personality traits. Cinque is effectively the owner of the rest of the cast, who are his pets.
 
Bonus optional ideas:
Part of the instinctive love and submission leads the males who have any connection or claim to a female to want to see Cinque have sex with them. Valerio sets up a foursome with Becky, Adel, and Couvert. Leaf wants to watch Cinque fuck the shit out of Leo (and maybe get his own ass torn up). And Gaul manages a trip with Cinque and Genoise up to the Sky Whale, just to see his subordinates and Aria all dripping Cinque’s cum together. As an oracle, Sharl can’t afford to lose her virginity yet, but anything else goes Some kind of mating season starts up, getting everyone horny and eager to get pregnant by Cinque

Plot unfolds in a way that Natsu doesn’t get sent to the future, and is instead actually contained in the Book of E.N.D., which makes its ways across the world. It acts kind of like a genie lamp, such that he has to obey the person who has the book. Eventually it makes its way into Mavis’s hands during Blue Skull’s attack on Red Lizard. From there, plot reaches the current era where people regularly try to get their hands on the book to get control of him. Primarily females because he’s slightly less prone to actively sabotaging them than when a male has the Book.
So a series of women having the Book of E.N.D. and control of Natsu, and using it for both power plays and sex. Natsu goes along with it because he kind of has to, but also because being an long-lived Etherious leaves him basically viewing it all as unimportant in the long-term. But one rule stands out above the others: Mavis is his favorite Master, because she was the first one who was kind to him, and the first one who used him as something other than just a beat stick to overpower enemies.

No, the mobile game said show is based on.

Eh, a lot of that comes down to Extra, which kind of plays fast and loose with a lot of universal mechanics. Like, the “representation of nameless heroes” thing is something that I’ve basically never seen brought up or taken seriously. As for why, maybe because it makes his power level unquantifiable, or because it goes against a preferred idea of him being (comparatively) a normal guy who just took wanting to be a hero too far and happened to have the right skill-set to go as far as he did, or because people think having EMIYA be the face of ALL the nameless heroes throughout history is just wanking. 
Even all the stuff with Kiara is debatable, because a)video game mechanics means you have to be able to fight and defeat the final boss, even if it doesn’t really work with the logic of the setting, b)the Sakura clones that she absorbed to become the final boss resisted from within because they wanted to save Hakuno, and c)Kiara became the demon god by using Andersen’s Noble Phantasm, which works on the basis of the story and Andersen’s own vision as an author, and he couldn’t allow something as convenient and simple as her becoming the “ideal self” she imagined just by absorbing them.
And the stuff that he did in that alternate timeline also came with having the Regalia that gives control of the Moon Cell. Compared to, for example, Karna, who did the same thing (soloing Nero and Altera’s factions, as well as the Velber) on his own abilities…
I like EMIYA. He’s one of the most interesting characters in Fate, and a better portrayal of the flaws in wanting to be a hero than most fiction. But within the universe, his role is to be Batman: smarter, more knowledgeable, and more prepared than basically everyone else. And making him that much stronger, making him actually physically comparable to other Servants is basically like making Batman from Krypton: now you have someone who is smarter than everyone, has a plan to defeat everyone, and is also strong and fast enough that he can still fight everyone without those things, and who really wants that? 

Eh, a lot of that comes down to Extra, which kind of plays fast and loose with a lot of universal mechanics. Like, the “representation of nameless heroes” thing is something that I’ve basically never seen brought up or taken seriously. As for why, maybe because it makes his power level unquantifiable, or because it goes against a preferred idea of him being (comparatively) a normal guy who just took wanting to be a hero too far and happened to have the right skill-set to go as far as he did, or because people think having EMIYA be the face of ALL the nameless heroes throughout history is just wanking. 
Even all the stuff with Kiara is debatable, because a)video game mechanics means you have to be able to fight and defeat the final boss, even if it doesn’t really work with the logic of the setting, b)the Sakura clones that she absorbed to become the final boss resisted from within because they wanted to save Hakuno, and c)Kiara became the demon god by using Andersen’s Noble Phantasm, which works on the basis of the story and Andersen’s own vision as an author, and he couldn’t allow something as convenient and simple as her becoming the “ideal self” she imagined just by absorbing them.
And the stuff that he did in that alternate timeline also came with having the Regalia that gives control of the Moon Cell. Compared to, for example, Karna, who did the same thing (soloing Nero and Altera’s factions, as well as the Velber) on his own abilities…
I like EMIYA. He’s one of the most interesting characters in Fate, and a better portrayal of the flaws in wanting to be a hero than most fiction. But within the universe, his role is to be Batman: smarter, more knowledgeable, and more prepared than basically everyone else. And making him that much stronger, making him actually physically comparable to other Servants is basically like making Batman from Krypton: now you have someone who is smarter than everyone, has a plan to defeat everyone, and is also strong and fast enough that he can still fight everyone without those things, and who really wants that? 

Honestly, as someone who has played FGO since very early on, a lot of the time there’s basically 4 reasons to like it: the characters, occasionally interesting bits of lore (Presidential Counter Force), the MEMES, and the addiction. It’s not exactly great mechanically (see the early problems with NPCs spamming dodge/invincibility skills, Merlin breaking the game so hard they had to add in a new mechanic to counterbalance him), but better than what I would have expected from a mobile game.
But at the end of the day, it mostly boils down to FGO being very, very good at making characters you didn’t know you wanted. “Jeanne d’Arc Alter Santa Lily” is a string of words I never imagined hearing together, but when I did, I knew I wanted her. Sure, a lot of characters are shameless pandering, but I don’t mind that. At the end of it all, I kind of just love seeing what they’ll come up with next (always hoping for a George Washington Servant, even if it won’t live up to the idea I have in my head), and can’t bring myself to dislike even the most shamelessly pandering Servants.
Except Merlin. Fuck him and his brokenness. 

Any word on progress, or if there’s anything else interesting coming down the pipeline anytime soon?
Also, of use for this story since Mordred is involved, and since I’ve been looking for it off and on for a couple months now, you know how Mordred’s final ascension form very definitely looks like she’s wearing no panties?

Well, I vaguely remembered seeing a picture that proved that, no, she does, they’re just not the sort that would be visible with that view. What’s more, it was something official, canonical, that couldn’t be argued with. So I tried off and on for a while to figure out where I saw that image, and I finally tracked it down. It’s not what I thought I remembered it being; I thought it was a concept art type thing, similar to what Type Moon always releases about Servants, but instead it came from the data mine when Mordred was first added to Grand Order. It’s a breakdown of her sprite, as in actually broken down into pieces, kind of looks like a taken apart action figure.

And there you have it, showing that Mordred does in fact wear some very skimpy underwear. Just a fun re-discovery I wanted to share.

Nothing ever really goes into that, unless it’s in Babylon, which isn’t translated, so...But Ishtar’s profile makes a point that her personality has been influenced by Rin so that the cruel part (i.e. the part that sent the bull after Gilgamesh rejected her) is suppressed and her good side is more prevalent. Also that, since she’s possessing Rin, a human, she doesn’t look down on humans like a god normally would.
And the description of how the relationship with the Master develops is: “She will come in contact with him in an affective and friendly manner, but just as 『a toy worth teasing』. But as their bonds become deeper, her natural disposition to take care of people and emotional weakness (she ends up empathizing with him) work against her, and he changes from 『a toy worth teasing』 into 『my precious contractor, whose future is worth watching over』.”

So it got clarified that, rather than using Extra Rin’s body, Ereshkigal and Ishtar are both using Rin’s body, and her hair turns blonde when Ereshkigal is in control because that’s the “proper” appearance for a goddess.
It was also explained that Tiamat can corrupt and control Servants, similar to what Dark Sakura does in Heaven’s Feel
 
And with Babylonia completed, the final battle was released and cleared within 3 days. As far noteworthy reveals…
 
As for where Grand Order goes from here, who knows, besides that they’ve mentioned another Valentine’s event. But as one person pointed out, even at the end of the “final” battle, Mashu is still only at NP level 3 out of 5.

So, in the time that this has been dormant, the seventh chapter of Grand Order has been released, introducing several new characters:
As for things these all lead me to think…
It’s specifically noted that Stheno and Euryale have no real combat strength except what the Servant container has, so young Medusa is probably similarly weak, which makes me think of all three being summoned like that, but as one Servant, similar to the Hundred Faced Hassan, or Anne Bonney and Mary Read. 
Tiamat as Beast could serve as another antagonist. She’s both supposed to be the mother of everything, and to destroy humanity as Beast, so maybe Shirou’s high CHA leads her to an Adam and Eve scenario, where she wipes out humanity and then they repopulate the world together.
It’s now possible to have a foursome with Medusa filling 3 of the slots. Also, she and her sisters can now fill 5 classes in a Grail War.
And I can see Rin’s goof-up, the presence of some artifact from Babylon left behind by Gilgamesh, and her/Shirou’s luck botching up her summoning, so while she does get Mordred, she also winds up with Ishtar using her body as a timeshare. Rin most of the time and during daily life, but when something threatens her (or just when Ishtar feels the need), she snaps into goddess mode. Possibly including Ishtar having sex with Shirou before Rin, then letting her wake up to the aftermath.

The Caster idea on the previous had me thinking:

Caster decides that, aside from Assassin as a guard dog, having a team to be out in the city fighting the War would be helpful, too. And, being tied into the leylines and being a mage from the Age of the Gods, she knows basically everything that goes on in the city, as long as she chooses to pay attention to it. By that, and by impressions gathered from Issei and Kuzuki, she finds Shirou summoning Saber to be a godsend.

Caster manages to mind-fuck Shirou (not that hard for her) into working for/with her. He has the same personality, and it has no effect on things completely unrelated to the War and magic, but once she wants him to do something, it happens. Probably just something such that he believes helping her is the best way to save people and be a hero. On top of that, she also put a magic kill-switch inside him, so that, if he gets to be a liability, she can get rid of him instantly, but also so he serves as a hostage. Saber is still in control of herself, but can't afford to oppose Caster or Shirou will die.

But after the first time she got too uppity, Caster decided to punish her, leaving Saber in a similar state to UBW: bound, dressed up like a doll, and under constant pleasure that never actually lets her orgasm. Until, after a day or two, when she begs for relief, as a reward, Caster lets Shirou have her. Only, since she's taken a liking to them, Caster insists Saber has to be a virgin for their wedding night, and Shirou is only allowed to fuck Saber's ass. Then she finally releases the spell keeping Saber from cumming.

Shirou is still in control of himself, just in a state where he wants to follow Caster's instructions. Saber hates Caster, but is broken-in and too attached to Shirou (and his dick) to disobey. Eventually, on top of her happy life with Kuzuki, Caster intends to "reward" Shirou and Saber for their assistance by giving them a similar "happy life." She especially looks forward to seeing Shirou impregnate Saber. Saber's "Knight on the Streets, Mind-Broken Fuck Slave in the Sheets" ending.

Alternately, Caster may also decide having even more help would be good, leading her to vaporize Shinji and Zouken and recruit Sakura and Rider, especially once she finds out how Sakura loves Shirou. Of course, they won't be allowed to break up her OTP, but having Sakura as a mistress and Rider as a slave isn't out of the question. Even better, since they're not wives, there's no need for Caster's romanticism, and they can get fucked in any way. And it makes for a great show: Saber, still being punished but getting more and more turned on and jealous as Shirou fucks Sakura silly, then Sakura orders Rider to join so she can enjoy Shirou, too. Only Rider doesn't really want to, and is being forced into it, until partway through when she realizes she's enjoying it. Rider's "Betrayed and Broken" ending.

Rin tries to oppose them, only to get captured, largely for Sakura's benefit. She gets enslaved, subject to Sakura's whims, who is intermittently a loving sister, a brutal master, and a voracious lover. Then she gets told about how Sakura was treated, the "training," and how, because of the worms, Sakura can't have children. "But that's okay, nee-san. Because you're here, and we're sisters. We can do it together. You, who couldn't even find love for your sister and shouldn't raise a child, just get pregnant and give birth to Senpai's children over and over and over, and I, who can't have babies of my own, will raise them and love them in your place." Rin's "Baby Factory" ending.

Illya is still around, still wants to kill Shirou, but with the overall team they've got, keeping Berserker occupied long enough to get to Illya isn't really a problem. Really, even with just Saber and Caster, it works. Although she could summon a different Berserker, like Mordred, another homunculus with daddy issues. Of course, while Mordred is fixated on Saber, Caster swoops in to use Rule Breaker on Illya, stealing Mordred away and capturing them both. Mordred gets the same treatment as Saber, only with the added bonus of seeing Saber acting like a pet, eager to please Shirou, and then seeing the King of Knights panting and moaning like a common whore while being fucked up the ass. She eventually succumbs to the pleasure and the idea of finally getting her father's love and approval, while also coveting the idea of stealing Shirou away. Illya gets well-treated, from figuring out she's the Grail and Shirou's sister. As she figures out he's a nice guy, but under Caster's control, SHE tries to control him, to help escape. But Caster expected that, so attempts by lesser magi to control him lead to violent responses, and Illya is punished by way of brutal rape from Shirou, under Caster's orders and the watchful eyes of everyone there: Caster, Saber, Mordred, the maids if they got captured, Rin, Sakura, and Rider if they got recruited. Saber realizes how broken she's become when she gets aroused by watching Illya, who she knew as a child and who is the daughter of her friend Iri, screaming and crying while being violated by Shirou, and that she loves Shirou in spite, or because of all of this. Once it's over, Illya recognizes Shirou's lack of responsibility, and realizes she loves her onii-chan. Illya and Mordred's "Big Happy Screwed Up Family" ending.

I’m pretty sure Shirou and Rin are 17 and Sakura is 16, because the standing joke was that Illya was the only one who was actually 18. Although Shirou’s age is totally vague and up in the air, given the fire.
 
I just imagine Kirei hurting himself laughing too hard when he finds out about Shirou NTR-ing Kayneth’s wife and Servant, remembering how Diarmuid unintentionally stole Sola-ui in the Fourth War.
 
And meeting the Demon Hunting Association? So can we look forward to Shirou meeting those families that are involved with it? The Ryougis, Asagamis, and Fujous? And the Tohnos, given they’re hybrids and have the last Nanaya?

But the Gamer Body makes the danger of Nerve Circuits a non-issue, since, instead of actually receiving the damage when he gets hurt, Shirou just takes HP damage. Combine that with proper skill leveling, and he can make it so the chance of screwing up is minimal, and even if he does, his HP will recover faster than it goes down, similar to how the protagonist of The Gamer distributes skill points and stats so his MP regens fast enough to keep a collection of buffs on permanently. 
 
On the note of the story, glad to see Shirou thinking about the consequences of showing off what his improved stats let him do, and actual internal conflict from Saeko, instead of just immediate and unstoppable shota lust. Though the developing Sense the Unnatural makes me curious, will Shirou wind up getting involved with the supernatural before the Grail War starts?

I mean, that would be all up to Ichasennin. They could be Mystic Codes or something, I guess.

Dammit, I always hate dealing with images on forums...oh, well, thanks for posting that since I apparently screwed it up.
 
I was rolling with the assumption that Class Cards wouldn’t be a thing, so they’d basically just be like Sella and Leys, two strong minions that could fight Masters but probably not Servants, along with the Kaleidosticks probably not showing up at all.

After a few days of nothing happening, something happened to make me think, “Hmm, you know, Julian Ainsworth from Prisma Illya could be a Master in this.” He’s got a crazy wish to save the world that could easily be displaced into this, with him recognizing the world’s declining state and wanting to be the hero who uses the Holy Grail to do it. He’s got an interesting enough skill set with Flash Air (basically Kawarimi from Naruto except switching anything with anything), even without letting him have any of the weird Grail related powers he has. Plus the whole “dolls animated by the spirits of the dead” could totally be used. The Ainsworth family is old enough to be able to justify having an artifact to summon just about any Servant IchaSennin wanted to use. And last and most importantly, the two Dolls he has already, Angelica and Beatrice…
 

 
I mean, Angelica is the closest thing we have to a canonical female Gilgamesh, so she’s always been great. But...this is official art, meaning Word of God, Beatrice Flowerchild do got the booty. And damn but she do.
 
Hell, could use Prisma elements with it, too. The Ainsworths picked up Miyu during the fire to use as a Grail to save the world, Julian is still working at that but also has her be a Master to try and stack the deck in his favor, but she escapes and winds up with Shirou, eventually Julian tries something against Shirou, winds up losing Angelica and Beatrice, too. So basically the same thing that will happen to Kayneth could happen here, with Julian losing his servants and everything to Shirou.

I mean, that's a valid concern. But thinking about it, I would place this as that wake-up call event. Celenike is actually a sadist who enjoys torturing young boys. It kind of gets glossed over in Apocrypha since her victims are Astolfo, who is so much more powerful than her that he yawns in the middle of it, and a random unnamed homunculus, but still. By comparison, Saeko has a taste for violence and sadism, but she's more or less a decent person that lives by society's rules and restrains herself. "To Celenike...patience and self-control were the same things as torture."
I would have this be the situation that shows the downside of Charisma. Where for everyone else, it made them more affectionate or more attentive to Shirou, for her, it would take her view from "What a cute boy, maybe I should pay him a visit after I get the Grail" to "Forget the Grail, I want that boy chained up in my dungeon now." Instead of making him a target of love and admiration, it makes him a target of her obsession and violence.
And that would be what I would say is the break-off point between her and Medb. Until then, they'd gotten along well enough, and she understands wanting a piece of Shirou after seeing him fight Hercules, and he might have been a little reluctant but he'd gotten into it well enough. But when it comes down to Celenike actually just wanting to torture him for her own enjoyment, no, she won't endorse that and betrays Celenike. Which leads into other conflict for Shirou's side, since this enemy Servant is now fading away without a Master but Shirou is insisting that they do something to help her since she saved him and also because it's Shirou. Plus the baggage of her history with Cu Chulainn and that she loves treasure and would still want the Grail for herself.

Well...maybe a little bit that, just because I do find it a disappointment how they sort of made that the focus of her character. Considering how much of her profile is dedicated to her being fixated on Cu Chulainn versus how much is actually about her...
But she also has Room lines that, summed up, basically say that for all the men she had, she never really felt love and doesn't really understand what love is. There's also some lines somewhere that say that what Medb really wants is someone that makes her fall in love with a look the way she makes men fall in love with her.
So basically, Shirou in this story with his high Charisma is pretty well suited to not just seduce Medb, but to make her embrace him as her husbando.

I don't think Jack would really care one way or the other about her outfit. Although since the Grail War starts in winter, Shirou would probably give her his coat the first time he saw her.
Yorimitsu's clones basically just seem to be a stylistic sort of thing. Servants actually summoning clones of themselves...the only one that does it is Hundred-Faced Hassan, and that's literally their whole thing. The other example that's come up was when the Edelfeldts summoned a Saber as two Sabers in the Third War, and that split the Servant's power. The elemental Irisviels were, in story, broken shards of the Grail that was destroyed that grew and developed wills of their own.
I certainly have no objection to Kuro showing up, but it's all up to Ichasennin and if it works within the story he's got.
And because I think it's a good idea to have it all clear and I enjoy making lists and charts and things...
Confirmed Servant/Master Pairs
1. Saber: Arturia - Master: Shirou
2. Caster: Morgan le Fay - Master: Kayneth
3. Berserker: Mordred - Master: Rin
4. Archer: Heracles - Master: Illya
5. Lancer: Cu Chulainn Master: Bazett/Kirei
6. Rider: Medusa - Master: Sakura/Shinji
7. Archer: Fem!Gil - Master: None
8. Avenger: Dark Iri - Master: Grail
9. ????: ???? - Master: ????
10. ????: ???? - Master: ????
11. ????: ???? - Master: ????
12. ????: ???? - Master: ????
13. ????: ???? - Master: ????
14. ????: ???? - Master: ????
15. ????: ???? - Master: ????
16. ????: ???? - Master: ????
17. ????: ???? - Master: ????
Confirmed Servant/Unknown Master
Temptress: Kiara Sessyoin - Master: ????(Someone who will get mind-broken. Current suggestions: May Riddel Archelot)
Unknown Servant/Confirmed Master
Assassin: Expendable/Some Hassan - Master: Sola/Zouken
Proposed Servant/Master Pairs
Ruler: Jeanne - Master: Caren Ortensia
Destroyer: Altera - Master: Sajyou Manaka
Phantom: Jack the Ripper - Rikudou Reika
????: Sita - Master: Miyu (Not Edelfeldt if she hasn't gotten picked up by Luvia)
Summoner: Medb - Master: Celenike Icecolle Yggdmillenia
Proposed Servants/Unknown Master
Hunter: Atalanta - Master: ????
Crafter: da Vinci - Master: ????
Shielder: Brynhildr - Master: ????
Idol: Stheno/Euryale - Master: ????
Tamer: Martha - Master: ????
????: Scathach - Master: ????
????: Medea Lily - Master: ????
????: Helena Blavatsky - Master: ????
????: Okita Souji - Master: ????
Proposed Servants that could also be used as Random Encounters
Tamamo
Kiyohime
Shuten Douji
Ibaraki Douji
Minamoto no Yorimitsu
Unknown Servants/Proposed Masters
????: ???? - Master: Luvia
????: ???? - Master: Fiore Forvedge Yggdmillenia
????: ???? - Master: Kuro/Chloe von Einzbern
????: ???? - Master: Bazett (after getting Lancer stolen)
????: ???? - Master: Olga Marie Animusphere
????: ???? - Master: Flat Escardos
????: ???? - Master: Cornelius Alba
????: ???? - Master: Atram Galiast
????: ???? - Master: Rottweil Berzinsky
...I think I got just about everything that's been brought up. If I missed anything, let me know and I'll add it.
EDIT:
Edited list as of July 18, per suggestions from myself and Wandering_Moth

Shuten. Face-sitting. Footjob. All I can say about that doujin is that there aren't enough "MUH DICK!"s in the world.
Manaka would live happily ever after. At least, that's what happens in her mind. I tend to think many yandere's don't make long-term plans or think very rationally, so she probably doesn't really think there's anything else to do or worry about once she has Shirou and there's nobody to take him away.
Phantom...put it this way, where most Assassins have Presence Concealment, Phantom Jack would have an ability closer to Mata Hari's Secret Intel. Instead of hiding like Assassins or just not being able to recognize her as a threat like Mata Hari, it would be that people just don't pay attention to Jack, unless she is acting as "Jack the Ripper." Barring people who would have a reason to notice her as something special and the ability to do so, it takes her doing something to draw attention to herself for people to notice her and not just dismiss her. Saber, for instance, would probably recognize her as someone dangerous by her Instinct, a Master as talented as Rin would probably notice something off about her, and someone she specifically wanted to interact with (i.e. Shirou) would definitely notice and remember her. But if she, say, went into a store and bought something or asked someone for directions, she would leave no impression, and within a few minutes, they wouldn't be able to describe her beyond "a female child." Basically, her Information Erasure works on people all the time, in addition to its effects after a fight. Other than that, her skills would basically be the same, I would think. Although it does lead to people actively disregarding her presence, so, I would say yes, something like sucking his dick under his desk at school would be something that could happen.
As far as her size and appearance, Rin is about 5'2-5'3, Jack is about 4'4-4'5, so Rin has about 9-11 inches on her (pardon my use of American measurements). Apparently, there was a case of Apocrypha Materials listing her height as 4'11, but that was retconned and declared an error. Also, considering that Rin is Japanese and Jack is (sort of) English, there's more of a consideration of difference. Rin is already slightly (1 cm) taller than the average Japanese woman. Jack, by comparison, is more than a foot shorter than the average height of women 16 or older in England today. And according to a site I found (admittedly just the first thing I saw by Googling), Jack's height is around the average height of an 8 or 9 year old in the UK today. Granted that humans as a whole have been growing taller as time goes on, she'd still probably be young, probably 10 to maybe 13 or 14 by 19th century London and given the malnourished street children she represents in canon.
Yorimitsu...yeah, I thought about her, too. Shirou could use a mother in his life, I'm sure. And I'm equally sure it would get more interesting when Yorimitsu and Dark Irisviel are both after him.
Yes, Miyu would be more or less the same age, maybe a little younger, just so Shirou has an Imouto-class heroine. Not by much, maybe a year or possibly fraternal twins. And yes, eventually I would say have Sita fall for Shirou.

You know, I was actually thinking, and several of the Masters and/or Servants I've wanted to suggest could be tied together to Shirou from the fire. Manaka could have seen it and been exposed to Angra Mainyu and corrupted during the fire, and become obsessed with Shirou once she found out he was the sole survivor.
I wanted to suggest Phantom Jack with Reika Rikudou as her Master, in which case I would suggest Jack is not just formed from the abandoned children of London, but also winds up being formed from the children who were victims during the Fourth War, from those Gilles and Ryuunosuke killed to those who died as a result of the fire. She instinctively recognizes Shirou as the last surviving victim from the Fourth Grail War, and identifies him as her "big brother," to be taken care of and protected. Reika lost someone important to her during the fire, and as a combined result of him doing something to help her during regular life, the relationship Jack has with both of them, and generally being a bit crazy herself, Reika latches onto the idea of Shirou as a replacement to fill a gap in her "family."
And the idea of Miyu with Sita popped into my head. Specifically, having Miyu as Shirou's sister who was entirely away from the fire, and who came looking for Shirou, only to find him after he'd already established a life as Emiya Shirou, so she can't bring herself to step into his life and say that they're family, and just stays away, watching him from afar. She summons Sita because they are both people who are separated from the person they love the most because of how much they love them.

One thing to consider is magic. Does Shirou still have it, to what extent, etc. And it's worth noting that, aside from magic tools like Claudette's sword and people who draw on divine power like the angels and nuns, pretty much everyone who uses magic in QB is more on the evil end of the spectrum. Swamp Witch and her minions, Funikura, Aldra while possessed by Delmore...even in Rebellion, while Aldra uses summoning magic, that's only because she's half-demon. So if Shirou did have magic, that would probably effect how he's viewed.

And if he were taken in, he'd have an unusual position. There's no blood relation, he's not family. He's not a bastard child like Claudette, there's none of that awkwardness. He's not family, so he doesn't get the same kind of special treatment a member of the noble Vance family gets, but he's also not a servant, so he gets treated pretty well.

Leina probably treats him like a brother without hesitation, just like she never treated Claudette differently as her half-sister. Admiration for his efforts to be a hero and generally just doing what he believes in, regardless of the rules and punishments. Thinks of him as someone to be like, then one of her more mature acquaintences on the road lines her up with the idea that she wants him. Then she winds up seeing the tournament as a way to prove herself to him.

He drives Claudette crazy with how he completely ignores any sense of standing, treating her just the same as he treats Leina and Elina, and with how he has a semi-respectable position as a ward of the family rather than an illegitimate child. The combined factors leave her wanting him, thinking he should be with her sisters, wanting to steal him from them, and resenting him. Having sex with him is her single act of rebellion against her family, her duty, and herself.

For Elina, he's more than a servant, less than a brother, so he doesn't get treated like dirt like servants, but he's supposed to cater to her anyway. It drives her crazy when he does something she doesn't want for her own good, like telling her to finish her vegetables as a child. But she adores him, and tries to make sure he feels the same about her, so at least while he's around, she treats servants like people instead of property. Not important people, but still better. Shirou would swear she's the sweetest of the sisters, and many would agree, with the caveat that she only is as long as he's around. Once he's gone, she's back to normal. As a result, some servants try to make sure they're around him as much as possible. Her ideal future has Leina succeeding their father, Shirou as Leina's husband, herself as Leina's bodyguard, Claudette in control of their military forces, and all of them in a mutual 4 way relationship.

Plus whatever encounters he has while traveling. Getting caught up in the Swamp Witch trio's shenanigans. Ymir being interested in his sword(s), especially if he still has any form of Projection. Encounters with any of the elves. Helping Tomoe and Shizuka find their way. Any pursuit of justice towards Aldra and what she's been up to. Nyx has complicated feelings towards him: Shirou was always kind to her, and while he was around, even Elina was tolerable, so she loves him. But once he was gone, Elina was so much worse than she was before he showed up, so she hates him for that. So she loves him, but also hates him, but since she REALLY hates Elina, she wants to take him from her.

At that point, sh, she might just make it so the jewel maid has the same effect so she or someone else constantly feels what it should be feeling. On the other hand, even though they're smooth, her gems are still cold, hard rocks, so, maybe not so good for the sexy-times. The slime does have precedent, though, with Lord El-Melloi II and his mercury maid. Plus, the more fluid shape would be easier to hide (in a jar, for example), and more malleable for the sexy-times. Just change the shape of the slime to be whatever she wants at that particular moment.
Now, in the spirit of the season...
It's Christmastime in Fuyuki, and all Shirou wants is for his two favorite people in the world, his dearest Onee-san and beloved Master, to get along for a little while. He just wants to spend the holiday with the two people most important to him, without them fighting like they always wind up doing. So he asks them, and with a little work to convince them (they would have said yes anyway, but think it's important that he not just think they'd tolerate each other just because he asked), the estranged sisters agree to spend the few days around Christmas at the Emiya house, trying to get along and doing the holiday thing.
Of course, they also see it a little bit as a competition, trying to establish superiority in the time they're both there. Dressing as sexy Santa or elf to try and get Shirou to pay more attention to them, mistletoe things. Of course, there's the inevitable gifts; aside from whatever else they might have gotten, Shirou also gets other more special gifts (being allowed to have either vaginal or anal sex with Rin after she'd been restraining him for a long time, something for Sakura. I'd imagine she'd already done basically everything she could think of with Shirou by this point). Rin includes a gag gift of a pair of her stockings, for Shirou to "use" when he's feeling the "urges".
Then Shirou gets upset with them for still competing when all he wanted was for them to get along, and he runs off. By the time he comes back, Rin and Sakura have realized they screwed up, feel guilty, and decide they really will spend the rest of the time they're there doing just what Shirou asked for: getting along and sharing in their domination of him. Double footjob, one riding his face while the other rides his dick, and with all the double femdom sex, there's peace in the house of Emiya for a while.

Sounds decent enough for the PWP.

New ones based on Prisma Illya:

First, while everyone else in the family is out doing their own thing, Sella and Leysritt are home, drinking. Nothing major, just that they like to cut loose once in a while. Sella's a lightweight, so while Leysritt is barely buzzed, Sella is smashed. Then Shirou comes home, and, having seen this before, goes to help Leysritt carry Sella to bed. But unlike all those other times, Sella looks at him and can't restrain herself anymore, and sticks her tongue down his throat. Leysritt takes this to mean it's open season on Shirou, and readily joins in. The next morning, Shirou and Sella are both horribly embarrassed. Irisviel approves of the situation, and expects it to continue.

Next: Illya, Kuro, and to a lesser extent Miyu all want their dear onii-chan. Mama-Iri notices this, and realizes that, if the much older and larger Shirou were to become a beast consumed by his perversion, he might wind up hurting them. Therefore, the only method to make sure nothing bad happens is to make sure Shirou is properly prepared to please his sexual partners, that the girls are properly prepared for him, and that they're properly supervised. Shirou gets dealt with in advance, since he needs the practice. He starts getting sent on "errands" where he winds up meeting up with Irisviel, who takes him and gives him detailed instruction and practical experience in every aspect of sex she can think of: oral, vaginal, anal, paizuri, and a bit of bondage, just in case. When she decides he's ready, he, Illya, Kuro, and Miyu find themselves trapped in what appears to be a love den with Iri, who explains that she is going to give the girls a demonstration of how sex goes, and then it's their turn. Miyu turns out to be a prodigy at this as well, though she wants Illya to be involved (she kept it a secret that she actually thought it was really exciting to have Illya watching her. Illya kept it a secret that she thought it was kind of exciting to watch her onii-chan and best friend together, with her being denied both of them. Kuro thought the whole thing was really hot, no matter which of the people there was involved). Kuro is delighted by the seal that makes her feel what Illya feels, since it effectively means twice as much sex for her. Plus, she's just all over anything lewd, so things like licking Shirou's cum out of Miyu while he fucks her from behind or her and Illya each sucking one of Iri's breasts while Shirou fingers them and Miyu rides his face are just what she wants. Illya is a little reluctant until she gets encouraged by her mother and the jealousy of knowing other people are fucking her onii-chan. Needless to say, they all end happily, and all the girls have an excess of prana. Kaleidostick and Class Card induced cosplay optional, but encouraged.
Third has spoilers for 3rei