(A/N)- A very small AU tweak of the Fate route scene where Illya has Shirou captured and held prisoner in her castle. Very small. Mostly only done for the whump and the sister reveal.

Disclaimer: *glances around* Nope, still don't own Fate/Stay Night. Darn.


Resentment

A splash of cold water to his face brought Shirou back to consciousness with a gasp. He coughed violently, hacking out stray droplets of water from his aching lungs.

Illya stood above him impassively with the upturned bucket, her red eyes glaring down with a cold expression at him.

"I did not say you could pass out," she growled. She tossed the bucket away with a clatter, then knelt down by his head, placing a hand on his cheek. "I want you awake for every moment of this, Onii-chan."

"I-Illya…" he croaked, his head still swimming, his arms aching from their position behind him, pinned between the chair he was bound to and the cold marble floor. He saw Illya give a smirk, and his pulse spiked. "Wait—"

She cut him off with another flash of that blinding pain. Shirou felt his body seize up, heard himself crying out as if from a distance as the million tiny needle-like stings pushing outwards from inside him overtook his senses again. His ears rang. His lungs burned.

As suddenly as she'd inflicted it, Illya let him have a reprieve. Shirou panted, his chest heaving, sweat and lingering dampness making the collar of his shirt stick to his skin. When Illya had described this torture to him—basically a complicated spell that, near as he'd gathered, overstimulated a magus's magic circuits to the point of pain—it had sounded almost harmless to him. He could never have imagined hurting this much.

The reintroduction to the white-hot agony had jogged his memory and now he could recall, all too well, the fire of it coursing through him, clawing at his insides, stealing his breath and making him thrash wildly until he felt himself tilt back with a dizzy lurch.

That was how he had ended up on the floor, he supposed.

Illya was behind his head now, hoisting the chair back up with a girlish grunt of effort. She huffed, her arms straining, as she pushed the chair back into its upright position.

Shirou groaned as the hard jostle caused the ropes to dig uncomfortably into his skin. Spots blossomed in front of his vision and for a long minute he couldn't focus.

"Honestly," Illya was snorting. "You really are a half-baked magus. I'm not even using the spell at its full potential."

She raised her hand at him.

"Wait Illya, s-stop…" he rasped out. "Why—" A fit of coughing rocked his frame with violent shudders. When he got his breath back he finished, "—why are you doing this?" He knew the girl could be cruel, despite her innocent facade, but this seemed a step too far even for her. All she had to do was let Berserker take a swing at him and he'd be done for, out of the fight for the Grail permanently. Why torture him? Why draw things out like this? He couldn't comprehend.

Her red eyes had a malicious gleam. "Because I hate you," she said pleasantly, smiling.

A glowing sigil appeared in her palm and Shirou was beset by another rushing onslaught of pain. His body rocked harshly in his seat, spasming, and he made the mistake of biting his tongue, giving a muffled yelp as his jaws clamped down and his own teeth pierced him.

When Illya stopped, his head hung forward limply, a dribble of blood dropping from his lips. Shirou breathed hard, swallowed and felt the hot copper tang sting his throat. His wrists ached, rubbed raw from the coarse rope.

"I know… that in this War… we're enemies…" he choked out. He shook his head weakly. "But still…" he said, "…Illya… I don't think… you're the type of person… that enjoys doing this."

He looked up at her, searching. She glowered at him, her brows narrowed, expression infuriated.

"I am enjoying this!" she insisted.

Shirou shook his head again. "No," he said, a soft smile gracing his lips. "If you really wanted to hurt me, you wouldn't have held back the first few times."

Her palm glowed. He yelped, a high-pitched screech, as another flash of pain—worse than the others—pierced through him.

"I was just letting you warm up," Illya spat, "for when the real pain comes."

Grimacing, Shirou shifted on his seat, trying to clear his head. Okay, maybe his guess had been wrong. His thoughts rolled about listlessly inside his pounding head as he tried to make sense of the girl's motives. This torment still seemed excessive for someone who was just an enemy in the Grail War. Something about all of this felt intensely… personal.

"Illya… what's your game with this?" he asked wearily. "Why don't you just kill me and be done with it, if you want me out of your way so badly?"

She didn't reply for a long moment. He looked up, and saw an oddly guarded expression on her face.

"…Shirou really doesn't know, does he?" she said softly. She gave a little giggle, lowering her hand to clasp it behind her back with the other one. She leaned over, beaming. "This isn't about the Grail, Shirou," she chirped. "It's about you."

Shirou blinked in confusion. "Me?"

"Mmm-hmm," Illya confirmed with a cheerful nod. Much less congenially she added, her eyes glowing dangerously, "And how much I despise your existence."

Foreboding hammered at his heart. "I don't understand." He raked his brain through the events of the past few days, trying to figure out what he could have done that would have given Illya such a specific grudge against him.

But then, he remembered… Illya had seemed to know of him before the Grail War…

Illya poked a finger into his chest, breaking his train of thought. "Because it's your fault, Shirou," she explained. "You're the reason he never came home."

"What are you saying?" Illya was uncomfortably up in his face now and Shirou leaned back as far as he was allowed. "Illya, I don't—"

"He found you and he forgot all about his family," Illya interrupted, starting to circle him. Her voice dripped with an eerie anger now. The pleasant smile was still in place but it was strained, faltering. "He forgot all about me. Everyone always leaves me in the end, you know," she said, in a melancholy kind of sing-song.

"What are you talking—" Something clicked inside his brain all of a sudden. "Wait…" Shirou's eyes widened. Illya had mentioned a "him". "He" had been her family, "he" had left and… found Shirou. No way, he thought. "Illya, was…" he asked, "…was Kiritsugu your father?"

She stopped circling and faced him. "Hmm. I guess you're not as dense as I thought," she mused. Her spine straightened proudly. "Yes, I was Emiya Kiritsugu's daughter… before he betrayed the Einzberns and never returned from the Grail War."

"So that makes us—?"

Illya shrugged. "Half-siblings I guess. It doesn't matter." A malicious grin had spread across her face. "Because you're not going to leave me, Onii-chan. Not like he did. I'm going to keep you forever. That's why it'd be a waste to kill you now." She raised her hand and let it glow ominously. "After all, I'm not done playing with you."

Shirou opened his mouth to speak but a burst of pain like a stab to his innards punched his gut and doubled him over. His eyes clamped shut, his jaw clenching, every muscle tensing as he waited it out. A desperate gasp filled his lungs once it was over. He could feel himself shaking, every intake of breath making him shudder. He resisted the urge to whimper. He wouldn't give Illya the satisfaction of knowing how much her spell was hurting him.

He focused instead on the indignant righteous anger bubbling in his stomach.

"Kiritsugu would never have abandoned you," he growled. "He wasn't like that! How can you believe he'd do such a thing?!"

All glee vanished from Ilya's face and she was truly angry now. "I don't believe it, it's true!" she snapped.

Shirou rolled his eyes. "Like hell it is." The man's mysterious trips abroad made a sudden amount of sense to Shirou now. Kiritsugu must have been trying to get back to see Illya but, for some reason or another, he had been prevented. "If you knew him at all you'd know that he'd never turn his back on someone he cared about," Shirou said.

Illya forewent punishing him for that statement with another round of pain, opting instead to just dart forward and slug him hard across the face. Shirou's head snapped to the side with the force, and he could feel blood pooling in his mouth again.

"Like you knew him so well!" Illya was shouting. "How much could you know about him, if he never even told you about me? You're just some orphan he pulled from a burning pile of rubble and took pity on!"

The next time her hand glowed was the worst yet; Shirou almost lost consciousness again, overwhelmed by the burning pain. When he came to himself and could think again, he decided it was time to put an end to this.

He muttered the words under his breath.

"Trace o—nnggh!"

He'd been unprepared for the sudden aftershock of pain. It felt a bit like trying to use a strained or pulled muscle; it didn't do anything and just hurt. Shirou blinked uncomprehendingly down at his lap.

"That won't work, Onii-chan," Illya trilled, dancing slightly on her toes. "Your magic circuits have been overloaded. They can't handle any other spells right now." Her smile of mean satisfaction was back, and her eyes glowed creepily bright in the light from the window. "You're all mine," she whispered.

Fear crept through his veins. Shirou squirmed, feeling truly helpless for the first time. He saw the sigil in Illya's palm beginning to light and flinched in preparation.

Pain assaulted his senses. The scream tore from him almost involuntarily, high and piercing, a shrill wordless cry of agony. Shirou had no control of his body, he couldn't think, he couldn't breathe, everything in him was ripping and tearing apart. His heart jolted, the pain stabbing deep into his chest. It felt like every molecule in his body was breaking, every bone fracturing and splintering. He wanted to beg Illya to stop but he couldn't even form words. All he could do was shriek, and wail, and endure.

And then suddenly it was gone. Shirou didn't even realize he had stopped hurting for several long seconds. His wailing died down.

Illya… must be letting me have a rest again, came the dull thought.

But no, Illya wasn't looking at him. She was wide-eyed on the floor, looking shocked. And there was dust and rubble blowing through the room, chunks of masonry and stonework sailing past him, as if something had blown out the wall to their left. Shirou tried to focus through blurry, swimming eyes. He blinked past his bangs towards the hole, peering through the gray dust.

Blue… Something blue, softly waving in the wind. Blue fabric.

Silver armor.

Golden hair.

Shirou's heart gave a leap even before the comprehension dawned on him, and his chapped lips were already parting to call her name.

"Sa… ber…" he whispered happily.

His head was still spinning dizzily but there could be no mistaking her, standing in the gap with her sword raised and her brows narrowed. It was Saber.

And she looked pissed.

"Run," she growled at Illya. "Before I change my mind about striking you down."

The girl gasped, scrambling to her feet, turning tail and running out the door. "Berserker!" he heard her cry before she disappeared.

Saber glared after her impassively, then her expression turned to worry as she moved towards him. "Shirou!" she cried. Her sword lowered as she cupped his face with one hand, looking over him in concern. "Are you all right?"

In truth, Shirou's head was still pounding, and his body was still throbbing and tingling all over with uncomfortable sharp pangs. But he ignored the pain to smile and tell her, "Better, now that you're here, Saber."

"Hold still," she instructed.

With a few quick swipes of Excalibur, she sliced through the binds holding Shirou to the chair. As he slumped forward, she caught hold of him.

"Can you walk? Illya will soon return, with Berserker in tow I imagine."

Shirou shook his head dully. He had already tried to push off Saber and balance upright on his own feet, but his legs felt like soggy jelly and all his limbs seemed weighted down. "I don't think I can. She took a lot out of me. Sorry, Saber."

Her arms clutched him tighter. She put Excalibur away, so she could better hold him. "No matter," she said, a soft smile ghosting across her lips. "I've got you. Don't worry." She gathered him up into her arms, as though he was light as a feather. "I'll get you out of here."

He reached up, clasping his hands behind her neck, a fuzzy darkness beginning to fog up his mind. "Thanks… Saber," he murmured, a dazed, dreamy look in his eyes.

Saber nodded, and then she was all business, turning swiftly on her foot and leaping from the second story bedroom Illya had stowed Shirou in down to the ground. She hit the ground running, bounding in great strides with Shirou clinging tightly to her as they made their escape.