Something I cooked up with Mereo Flere and Fallacy. Revised thanks to Gauss.
Life was good, Saber supposed. In her experience, the magi were either dicks or put dicks where dicks didn't belong. She was lucky enough to find not one but two magi who she found more than likeable and perhaps even loved. After the whole torrid affair of the Holy Grail Wars of Fuyuki, the three of them moved to London, the capital of the nation that was once her home. Even though it was vastly different from her time, she still enjoyed being on her native soil and basked in this moment of joy, but…
But sometimes, just sometimes, she wished her—what could she call them? Lovers? Friends?—magi would be less… Saber couldn't really think of the word. It was really only Shirou, she amended. Sometimes, she found herself more frustrated with him than she ever was with Merlin. She hadn't thought that would have be possible but this was one of those times.
She was currently standing in the kitchen, Shirou's usual preferred room in the roomy apartment they shared, with nothing but some rather expensive, white-laced lingerie covering her body. The garter belt was rather itchy for her since it was perhaps the second or third time she had worn it, and the thigh-highs were rather uncomfortable, but for her sake and Shirou's, she endured it. Rin was behind her in a similar, black outfit, fondling her in a rather increasingly stimulating manner. But all of that seemed to fall rather flat for the one they were performing the lap dance for.
"Shirou, it's time to… replenish my mana," Saber tried for the hundredth time, strutting around her former Master as sensually as she could. Normally she walked and stood straight like a man, but in the privacy of their bedroom, she added an extra sway to her hips as she sashayed around.
"Huh?" Shirou frowned up at her. Behind Saber, Rin buried her face into her palm silently at Shirou's response.
"Shirou," She repeated to him through gritted teeth, "Replenish my mana."
"But Saber," He replied obliviously, still calling her by that title even after he gained some mastery over English, "Isn't Tohsaka supplying you with—"
"GAH!" Rin snapped, having endured this for the past half hour, and pinned Shirou down on the ground.
Shirou's eyes shot wide open as he gasped, "R-Rin?"
"Saber! I'll hold him down," Rin cried with a maniacal expression that caused Saber to shiver, "You strip him!"
"W-wait!" Shirou whimpered as Rin's fingers snaked down and stimulated him and caused him to shriek. But before he could utter another sound, a bright light surrounded them. A moment later, they disappeared.
Emiya Kiritsugu surveyed the scene within the Einzbern Chapel, silently marveling with his wife at the simplicity of this ritual that would grant his life's ideal. His expression was cold and grim, showing none of the anxiety he suppressed at this monumental event. As his beloved wife Irisviel finished her preparations for this ritual, carrying the sacred relic Avalon to the center of the circle they had prepared, Kiritsugu's resolve held firm, 'My ideals… my dreams rely on this summoning.'
The ritual itself was simple and quick. With a flash of light that came with the power used in this summoning, his Servant began to appear. That was when all the alarms within Kiritsugu's head went off and exploded.
Instead of a royal knight wearing medieval armor or even a king garbed in gold and blue, something else appeared. Something that shouldn't have appeared had appeared.
The first problem Kiritsugu noticed through the lightshow was that instead of there being one human-like body, there were three. The second problem he noticed was that none of them were wearing armor. In fact, they seemed to be wearing almost nothing. There was a boy with red hair pinned down by a girl who looked to be of mixed, Asian descent with a petite, European girl tugging on the boy's underwear.
The moment all the smoke had cleared, the blonde girl had let go immediately in surprised shock. Their attire stuck out for Kiritsugu, but he speculated that it was possible that King Arthur's clothing had changed in the Throne of Heroes. The redheaded boy was wearing nothing other than that pair of boxers, which Kiritsugu was pretty sure did not exist in Arthurian times. The Asian girl was wearing nothing but elaborate, black laced underwear made from… silk, perhaps? The blonde girl wore something similar but white.
Kiritsugu's first thought was that perhaps he had summoned King Arthur when he was still young. Then the European girl tried to speak up, saying something that sounded like 'are you my master', but her voice was drowned out by the boy, who whimpered something between an "Eep!" and "Daddy!"
Everything seemed to still, as if time had frozen. Irisviel was almost glowing with a blush and trying her best to cover her eyes. The brunette girl's expression turned cycled between confusion, horror, and curiosity before settling on something even Kiritsugu could not read. The blonde girl just stumbled and fell onto the boy's chest. Kiritsugu stood and stared, shocked, before he managed to shake himself out of it.
Kiritsugu frowned and his analytical mind, which knew that King Arthur must have been a man, deduced that, 'At some point in my future, did my Innate Time Manipulation fail and send me to England in 500 AD, where I became Uther Pendragon?'
The brunette girl's grumble, which sounded like, "Hey, Saber, I'm your Master!" flew right over Kiritsugu's head.
Saber wanted to groan. No, she wanted to do more than that! She wanted to walk up to the World and smack it around for putting her through her life. Did this even count as her life anymore? She put that philosophical question aside for the immediate matter at hand. There she was, on top of Shirou and just moments from finally pulling his underwear off when this happened.
This… she remembered this quite clearly. It was the war she had participated in just before she finally met her lovers. And she didn't want to remember it at all.
'Oh, no! Oh, no… no, no, no!' Saber's eyes filled with panic, though unnoticed by everyone else.
Steadying herself, she tried to act composed and fall back on her old reaction towards this, which was to ask, "As you have summoned me, I have come. Are you my Master?" She only grumbled part of her question out before being interrupted by Shirou, who whimpered loudly enough to echo through the Chapel, "Daddy?"
Saber felt dread sink into her heart as she watched the gears turning in Kiritsugu's head (So that's where Shirou inherited that from!), she heard Rin protest, "Hey, Saber, I'm your Master!"
Then there was a pause, in which Rin's eyes began to sparkle. Saber's heart skipped a beat as her panic redoubled.
"Wait!" Rin cried loudly, "That means I qualify for Caster!"
Saber cringed; there were sparkles that looked like something out of a kaleidoscope surrounding Rin now, as if Rin had floated into another realm. 'No', Saber quickly amended. She was even shinier than that; Rin was sparkling even more than those vampires from that movie that Sakura liked so much. Even Rin's eyes seemed to have turned into tiny stars.
'Quick!' She thought as she squeezed from between Rin and Shirou's sweat-covered bodies and picked herself up, 'I need to fix this!'
"W-wait, upon your summoning, I have come!" Saber called out, "I am Servant Saber."
This seemed to go over Kiritsugu's head as he turned purposely away from her and stared at Shirou, "Hmph."
Saber frowned and tried again, "I-I am King Arthur, the one you have summoned…!"
Kiritsugu stroked his chin for a moment before narrowing his eyes at Shirou and muttering, "So King Arthur had red hair. This is not consistent with our historical records, but it will work."
"H-hey!" Saber suppressed her pout and tears and tried again pointing at Shirou and shouting, "I'm King Arthur not—"
"That's impossible," Kiritsugu mumbled, not even bothering to turn towards her. "There's no way that King Arthur was a woman."