Sakura and Shirou
Shirou looked down at the bound girl with a sadistic smirk on his face, knowing he would immensely enjoy what was to come. Sakura, meanwhile, was utterly petrified of what was to come. She had asked to be tortured horribly, after all, to be taken beyond her very high limits of tolerance for pain and humiliation and, now, she was bound helplessly, ready for her tormentor to do whatever they wished to her. She had no idea what had come over Shirou, he had previously been adament about his unwillingness to torture her like this but, honestly, she didn't mind. If she was going to suffer, it may as well be at his hands. And, besides, she had hurt him too, he deserved to be allowed to punish her if that was what he wished.
Emily, meanwhile, simply watched on with excitement as Shirou did the job demanded of him, locking Sakura into the pillory. Then, with the girl suitably trapped and ready for whatever punishment they might dish out to her, she spoke, getting into character.
"Isn't this fitting though, for someone who took everything from me", she said, the anger clear in her voice. "I'm going to pay you back for the pain you've caused me!"
Sakura was overcome with fear and self-loathing at her words, looking down at the floor with a look that combined sadness and fear at what was to come. She knew, of course, that this woman had not really been a victim of her actions in the Grail War, but that was beside the point. She was here to represent the victims who could never even know what she had done, let alone punish her for it. Every word she said was said on behalf of those she had hurt, every torture she inflicted and every humiliating act done on their behalf. Yet, however much she knew she deserved this treatment, it still absolutely petrified her. She was practically shaking in her bindings, knowing that there was now nothing she could do to escape, short of somehow convincing Shirou she had changed her mind.
Shirou was now even more aroused as he watched Emily walk over to the wall to find suitable implements, knowing that she was very much getting into her role, and that Sakura's punishment would be severe. However, she had not yet been particularly forceful with him, expecting him to follow her wishes more-or-less willingly. He hoped that she would soon do as he wanted, and force him to obey her, before he felt like it was stretching plausibility for him not to fight back.
"She won't be needing her clothes anymore", she called to him, "Remove them from her however you want to."
Shirou frowned at her words. Part of him wanted to simply refuse the order, to make her "force" him into obeying but, if he was to turn on her right now, he would undoubtedly win, and that would ruin the whole thing. And, as much as he disliked her lack of forcefulness, the idea of undressing his captive girlfriend was very definitely a turn-on. So, reluctantly, he approached the obviously-frightened girl, pondering how best to undress her.
"No, Senpai! Please, no, let me go!" Sakura said as he approached, the fear overcoming her once more, making her desperate to back out of the punishment she knew she deserved.
Normally her words would have tugged uncontrollably at Shirou's heart-strings but, right now, he had a single-minded focus. All he cared about was fulfilling his fantasy to be forced to torture Sakura, and listening to her went against that.
"I'm sorry", he lied, "If I disobey, she'll make you suffer even more."
A quissical look came over Sakura's face on hearing his words. Had he agreed some sort of roleplay thing with Emily she did not know about? Regardless, it was not good for her at all.
No, I deserve this. If Senpai wants to punish me as well, then I should not deny him that right, she thought.
Meanwhile, Shirou began working on undressing the captive girl. The skirt was simple enough to remove, he simply undid the side zip and allowed the garment to fall uselessly to the floor. He took a moment to admire her panty-clad rear before deciding that he would rather see her fully exposed. Grabbing hold of the simple pink panties, he pulled them downwards until they were free of her thighs, allowing them too to drop to the floor. Taking another few moments to admire her ample and exceptionally-beautiful rear, he pondered how best to remove her top, before figuring that he could probably just tear it off.
So, he grabbed hold of the bottom of the shirt and, putting all of his strength into it coupled with a little self-reinforcement, he tore upwards until the shirt was ripped cleanly in two. Then, he took hold of each arm in turn and ripped that as well, leaving the shirt to fall uselessly to the floor, Sakura now clad in nothing but her bra. This he quickly unlatched, aided by the fact that Sakura had been thoughtful enough to wear easily-removable underwear, and allowed it to drop the the floor also.
His erection grew further as he admired her beautiful bound form, her fear evident even from where he was standing. As he did so, Emily returned from the wall, ready to begin Sakura's torment. Before Shirou even knew what was happening, he felt a collar being fastened to his neck, and a cane thrust into his hands.
"Use this however you see fit", she said, "but make her suffer for what she's done."
Shirou's erect penis was now throbbing with desire, the girl's new-found attempts at assertiveness and forcefulness turning him on no end, as was the thought of what he was about to do to the girl he loved.
"If you refuse, however", the girl continued, tugging on the leash and brushing the whip gently against his back, "I will not be pleased."
Shirou shuddered from excitement as he brought the cane to rest on Sakura's ass. Sakura, meanwhile, felt nothing but fear of the punishment she was about to receive.
"Sorry, Sakura", he said, the huge erection that he was sporting a significant hint that he did not truly mean it, "but I have no choice but to obey her for now."
With that, he drew back the cane and brought it back down on Sakura's ass, as hard as he could manage.
"AAHH!" the captive girl yelped as the cane impacted into her bare backside.
"N..no..., Sen...pai... please", she moaned.
Shirou turned to Emily, glaring at her angrily as he raised the cane once more.
"I will make you pay for this!" he spat. "If you let your guard down for even a second, I will inflict every one of these tortures on you ten times over".
With that, he brought the cane down once more, causing the captive girl to let out another pained scream, Shirou's arousal growing despite his supposed reluctance.