Sakura and Shirou
Sakura was confused and a little bit irritated by the clueless expression on her sister's face. Had Rin really forgotten who she was? Her own little sister?
Before she could say anything, however, the girl suddenly had a flash of recognition, and began to greet her happily, albeit a little robotically. But, then, things began to get weird, as the girl bowed, apologising profusely and insulting herself in the process. Sakura was surprised, amused and a little embarrassed by the display, wondering what exactly was happening. Shirou, meanwhile, could barely suppress a giggle at the sight, something that he felt might have come straight out of one of Sakura's darker fantasies.
But, before Sakura or Shirou could say anything, the girl's expression and tone changed once more, this time to something far more robotic. Addressing Sakura as "master", she asked what the girl wanted. For a few moments, Sakura looked at her, dumbstruck, before she came to a realisation. The girl's bizarre behaviour, the robotic manner in which she was acting and the weird, shadowy taint all pointed to one thing. This girl was some kind of very advanced shadow familiar. And, given the manner in which she was reacting to Sakura, Sakura's own history with her sister and her knowledge of what she might potentially be capable of, she had no doubt that this girl was the creation of an alternate Sakura. One who, seemingly, had even more issues with her sister than she did.
For a moment, Sakura hesitated. The last version of her that she had met had been completely insane, attempting to kidnap Shirou. And making a shadow maid that looked like Rin and humiliating her hardly pointed to sanity, either. At the same time, though, it wasn't really harmful, and it was something she could maybe have seen herself doing, once, if she had the capability. And finding a potential ally would be useful. So, she addressed the familiar with a smile.
"Excuse me, but can you tell me where the person who created you is?" Sakura asked. "I would like to talk to her."