Shirou and Rider
Shirou looked at Sakura with confusion as she responded to his question about Rin's presence by asking about his own.
Eh, what? We came here together, how can she not know why I am here?
Before the thoroughly-confused Shirou could ask Sakura for an explanation, however, Rider spoke up, explaining that this Sakura was not, in fact, his wife, and was far younger than him, with her own Shirou.
Shirou looked up at Sakura again. With his eyes now somewhat acclimatised to the darkness, he was able to make out some features, and he did notice some slight differences, although it was difficult to tell in this light. Before he could get a better look, though, he felt the rather-familiar feeling of one of Sakura's shadow tentacles wrapping around his head, blindfolding him.
Eh? What is she doing?
Shirou was confused by her actions. What was it that she didn't want her to see. And, if she wasn't his Sakura, then where did she come from?
Shirou pondered it for a moment, before coming to a realisation.
Of course, they must be the versions of Sakura, Rin and Rider from this world. But, why the blindfold?
There was definitely something odd going on here. The only thing he could think of an an explanation was Rin's state of dress but, even supposing that this Sakura still felt insecure enough that she was worried him seeing Rin like that might cause him to go after her instead, she had her own Shirou and was clearly not interested in him in that manner, so why would she need to stop him seeing Rin in a towel?
Still, at very least, the fact that Rider was around and Sakura was in a relationship with Shirou suggested that Zouken was probably gone, which was good news. He just hoped that Rin had actually sent them to the right dimension and, also, the right time. Having to wait around for 20 years for Rider to appear would be extremely bad.
Whilst he was considering the situation, he heard Rin make a comment on the joys of alternate realities, whilst Sakura addressed him once more.
“That’s right, we’re not married yet! You haven’t even proposed to me!” She said. “Wait-- Do you have your own Sakura?”
Shirou nodded but, before he could give a more thorough response, Rin spoke again, whilst Rider looked at the scene with some amusement, taking subtle glances at Rin when she got the opportunity, careful not to let Sakura see what she was doing.
"I assume this is Faust's handiwork”, she said, before attempting to calm his automatic repair system enough to allow her to heal him.
Faust? Who is that? Shirou thought, wondering what the hell Rin was talking about.
As she was healing him, Shirou felt a new, extremely familiar magical signature appear at the top of the stairs.
"Sakura?" the newcomer said in a very familiar voice.
That must be her Shirou..., he thought.
And, sure enough, Shirou quickly noticed the newly-arrived magical signature approaching that of Sakura.
"Sakura, are you okay?" the other Shirou asked her, presumably hugging her as he did so.
Shirou knew that he needed to explain things. And, preferably, get Sakura to remove this blindfold. He probably could manage to cut it off, but that would likely upset her. It was far better to just ask. First, though, he needed to explain himself. And to apologise for the level of passion he had previously shown her.
Shirou looked at Sakura sheepishly, feeling somewhat guilty for kissing her without permission, and spoke.
“I apologise for my actions, Sakura. I do indeed have my own Sakura, we came to this world from our home dimension to find our Rider, and got separated in transit. I thought I might never see her again, which would make her sad, and when you appeared I mistook you for her, hence my passionate reaction”, he said.
“Anyway, it's nice to meet you. It is good to know that you are well, and that your family is here for you”, he continued, looking in her direction with a genuine smile on his face. “Could you please remove this blindfold, though? It is somewhat discomforting to not be able to see what is happening.”