Mitsuzuri Ayako was rather concerned. All that morning, she'd been noticing odd things, like cars changing colour, make, and/or model between one glance and another, animals staring fixedly at her and then vanishing into shadows that shouldn't have been there, or her house briefly seeming to be on the wrong side of the street. Also, her memories were off - she recalled being attacked on the way home, on a day that she also remembered making it home unmolested, yet she still had a scar from where she thought the blindfolded woman had bitten her - after apologising for it, oddly enough. The scar was itself wrong, because it was far better healed than the time that passed would imply. She recalled Shirou apologising for an insensitive remark he'd made (that she hadn't been there for, but he was apparently sure someone would tell her about), but she also remembered an entirely different, much briefer conversation. She remembered being Shirou's girlfriend for a while, seeing him die rescuing people after an earthquake, and then a guy named Archer asking her if she was his Master. The most disturbing one was the memory of committing seppuku - though she couldn't recall the reason, or even what haiku she wrote - and being both proud and relieved that Shirou got the beheading stroke exactly right, on the first try.
In the park, she bought a shaved ice, and nearly dropped it when she turned around - there was a large monument, there, that definitely had not been present a minute earlier. It was a tall, five-sided stone obelisk, with writing on it in fifteen languages (three to a side). The writing, at least in the languages she could read, said "To those who gave up all that they had been, were, or ever could be, so that we might exist at all." No-one remembers it appearing, or being set up, but a few people think its always been there.
After the obelisk appeared, the strange events ceased, but the contradictory memories remained. Knowing that Shirou and Rin are connected to the weirdness in town, she decides to head over to Shirou's place, to see if she can get some answers - and reassure herself that he was alive.
He was alive, but he was not entirely certain that that was a good thing. He had Ilya, Rin, Saber, Sakura, and Rider living with him, and all of them have contradictory memories, some more clear than others. Shirou has very clear memories of the Fate, UBW Good, and HF True scenarios, as well as less clear memories of several others - including a few where Ilya made him her toy. He remembers Tracing the key to the Gate of Babylon, and looting the King's Treasure House with Rin and Archer (Saber didn't approve). He was rather impressed that the second fight with Gilgamesh had not been a curbstomp in their favor, even if they did win. He has the Emiya Crest, which he was sure had been buried with Kiritsugu, and recalls using it in some versions of the War. He also recalls Ayako committing seppuku, and is relieved to see her alive. As best he can tell, he remembers all the timelines that the others do (but not always with the same clarity), as long as he was alive. In some timelines, he has Archer's memories instead of, or as well as, his own.
Ilya recalls something like the Fate route, but involving more actively helping Shirou (and playing house with him), because she had seen several anime since arriving in Japan, and had seemingly internalized the idea that Defeat Equals Friendship. She remembered being raised as Shirou's younger sister, encountering the Ruby Kaleidostick, and becoming Magical Girl Prisma Illya. She also recalled Kotomine ripping her heart out, and a few other unpleasant things, but could not recall where her new body came from. She liked it, when she looked in the mirror, she could almost see her mother looking back at her, but the differences in size and weight distribution made her clumsy.
Rin and Saber had clear memories of the UBW Good scenario, and recall HF up to being eaten (Rin's rather glad she can't remember anything after that), as well as a few others. Rin recalls either Saber or Sakura buying her at an art auction, but hopes that was a dream; failing that, she hopes the large audience at the auction doesn't remember seeing her naked. She and Sakura both recall the Childcare is War timeline - in fact, large swathes of Rin's lonely childhood memories seem to have been replaced by it. Saber recalls a world where she never found out about the Grail's corruption, until after she made her wish. In that timeline, she became Merlin's apprentice, but the guy who became king in her place turned out to be a tyrant, forcing her to reveal her heritage, and rule as the Witch-Queen of Britannia. Not everyone was terribly happy about that, and she recalls being summoned as Caster, and learning that she was reviled after her death, mostly by the Church - though like Vlad the Impaler, the descendents of her subjects, mostly in Wales, still prayed for her return in times of strife. She remembers that art auction quite vividly, as well as the fun they had, afterward.
Sakura and Rider have the clearest memories of the HF True scenario (and Sakura has the increased prana from it), but for some reason, Sakura has no clear memories of her horrific homelife (something she hopes means that this is the work of a benevolent force), these being replaced by a mix of Childcare Is War, and a strange timeline where she and her sister were raised as geisha and witches, and their contracts were bought by the Daimyo Fujimura Raiga, as a gift for one of his samurai, Emiya Shirou. She also recalls that art auction, but isn't mean enough to tease Rin about it - especially as she thinks it might have been a euphemistically named slave auction. She remembers the timeline where Shirou died, and then learning that the Archer in the Fifth War was another Shirou - she and Ayako shared him, after they won the War, while Rin went of to London with Saber. Rider remembers attacking Ayako on Shinji's orders, more than once, but also recalls a world where she never died, and another where Sakura was Caster, and summoned her the way Caster Medea summoned False Assassin.
All of them, Ayako included, have vague, fragmentary memories of fighting impossible enemies. They don't recall what the enemies looked like, or why they were impossible, just that they were. When they start to check, they find that many magic-users, official or otherwise, remember the Impossible Enemy, and very few non-magi do - only those with strong emotional connections to a magus, or very high levels of combat skill, luck, or both. Relatively few magi, or other paranormals, have contradictory memories that don't involve the Impossible Enemy, and no-one recalls why the enemy was impossible, or what they looked like.
A lot of people have skills and knowledge they don't recall learning, or powers they didn't have, before. A very few people have active magic circuits, or even Crests, who weren't even aware of magic, before. A few are alive who died some time ago (Matou Shinji is still dead, but has two gravestones, in separate cemeteries, with different dates), and some have been dead for years, who were alive, yesterday. The vast majority don't notice the contradictions, but everyone with a connection to the paranormal does.
I don't have a clear idea on WTF happened, beyond what's written, here. Its up to the author, as there are multiple possibilities, but its a mystery that I think they'd want solved. You could also do harem comedy as a subplot, or main plot, or go full lemon.
So, any takers?
In the park, she bought a shaved ice, and nearly dropped it when she turned around - there was a large monument, there, that definitely had not been present a minute earlier. It was a tall, five-sided stone obelisk, with writing on it in fifteen languages (three to a side). The writing, at least in the languages she could read, said "To those who gave up all that they had been, were, or ever could be, so that we might exist at all." No-one remembers it appearing, or being set up, but a few people think its always been there.
After the obelisk appeared, the strange events ceased, but the contradictory memories remained. Knowing that Shirou and Rin are connected to the weirdness in town, she decides to head over to Shirou's place, to see if she can get some answers - and reassure herself that he was alive.
He was alive, but he was not entirely certain that that was a good thing. He had Ilya, Rin, Saber, Sakura, and Rider living with him, and all of them have contradictory memories, some more clear than others. Shirou has very clear memories of the Fate, UBW Good, and HF True scenarios, as well as less clear memories of several others - including a few where Ilya made him her toy. He remembers Tracing the key to the Gate of Babylon, and looting the King's Treasure House with Rin and Archer (Saber didn't approve). He was rather impressed that the second fight with Gilgamesh had not been a curbstomp in their favor, even if they did win. He has the Emiya Crest, which he was sure had been buried with Kiritsugu, and recalls using it in some versions of the War. He also recalls Ayako committing seppuku, and is relieved to see her alive. As best he can tell, he remembers all the timelines that the others do (but not always with the same clarity), as long as he was alive. In some timelines, he has Archer's memories instead of, or as well as, his own.
Ilya recalls something like the Fate route, but involving more actively helping Shirou (and playing house with him), because she had seen several anime since arriving in Japan, and had seemingly internalized the idea that Defeat Equals Friendship. She remembered being raised as Shirou's younger sister, encountering the Ruby Kaleidostick, and becoming Magical Girl Prisma Illya. She also recalled Kotomine ripping her heart out, and a few other unpleasant things, but could not recall where her new body came from. She liked it, when she looked in the mirror, she could almost see her mother looking back at her, but the differences in size and weight distribution made her clumsy.
Rin and Saber had clear memories of the UBW Good scenario, and recall HF up to being eaten (Rin's rather glad she can't remember anything after that), as well as a few others. Rin recalls either Saber or Sakura buying her at an art auction, but hopes that was a dream; failing that, she hopes the large audience at the auction doesn't remember seeing her naked. She and Sakura both recall the Childcare is War timeline - in fact, large swathes of Rin's lonely childhood memories seem to have been replaced by it. Saber recalls a world where she never found out about the Grail's corruption, until after she made her wish. In that timeline, she became Merlin's apprentice, but the guy who became king in her place turned out to be a tyrant, forcing her to reveal her heritage, and rule as the Witch-Queen of Britannia. Not everyone was terribly happy about that, and she recalls being summoned as Caster, and learning that she was reviled after her death, mostly by the Church - though like Vlad the Impaler, the descendents of her subjects, mostly in Wales, still prayed for her return in times of strife. She remembers that art auction quite vividly, as well as the fun they had, afterward.
Sakura and Rider have the clearest memories of the HF True scenario (and Sakura has the increased prana from it), but for some reason, Sakura has no clear memories of her horrific homelife (something she hopes means that this is the work of a benevolent force), these being replaced by a mix of Childcare Is War, and a strange timeline where she and her sister were raised as geisha and witches, and their contracts were bought by the Daimyo Fujimura Raiga, as a gift for one of his samurai, Emiya Shirou. She also recalls that art auction, but isn't mean enough to tease Rin about it - especially as she thinks it might have been a euphemistically named slave auction. She remembers the timeline where Shirou died, and then learning that the Archer in the Fifth War was another Shirou - she and Ayako shared him, after they won the War, while Rin went of to London with Saber. Rider remembers attacking Ayako on Shinji's orders, more than once, but also recalls a world where she never died, and another where Sakura was Caster, and summoned her the way Caster Medea summoned False Assassin.
All of them, Ayako included, have vague, fragmentary memories of fighting impossible enemies. They don't recall what the enemies looked like, or why they were impossible, just that they were. When they start to check, they find that many magic-users, official or otherwise, remember the Impossible Enemy, and very few non-magi do - only those with strong emotional connections to a magus, or very high levels of combat skill, luck, or both. Relatively few magi, or other paranormals, have contradictory memories that don't involve the Impossible Enemy, and no-one recalls why the enemy was impossible, or what they looked like.
A lot of people have skills and knowledge they don't recall learning, or powers they didn't have, before. A very few people have active magic circuits, or even Crests, who weren't even aware of magic, before. A few are alive who died some time ago (Matou Shinji is still dead, but has two gravestones, in separate cemeteries, with different dates), and some have been dead for years, who were alive, yesterday. The vast majority don't notice the contradictions, but everyone with a connection to the paranormal does.
I don't have a clear idea on WTF happened, beyond what's written, here. Its up to the author, as there are multiple possibilities, but its a mystery that I think they'd want solved. You could also do harem comedy as a subplot, or main plot, or go full lemon.
So, any takers?