He scrunches up his nose for a second, trying to think: had there been anyone in Chaldea like this where he was from? Mm - no, he's almost certain of it, he's never seen this woman. Nene puts on his best friendly face and offers out one small, scarred hand (of course, she doesn't have to take it). "I - uh. Hi. I'm the - er, Shielder that sort of crashed here. I don't think I ever met someone like you where I'm from, so! It's very nice to finally meet you."
The new Shielder. She’d heard about him, though not been materialized to meet him until now. The boy seemed young, younger than she had thought him to be, and held what within her eyes was complete non-preparation for their current situation, for everything they had and were yet to face. Illyasviel could not understand how someone like him had survived long enough to end up here.
“I had heard of you.” Yet, she wasn’t completely without manners and extended her hand to shake his. Even now she had the status of an Einzbern to uphold. “You may call me by my class - Caster.” But even then she still had her reservations not to simply reveal her name to someone who seemed not to have any clue of the Einzberns.
Any magus worth their salt would know who she is with a simple look, and thus any who could not did not deserve to know.
“I am not from the Throne of Heroes, thus not existing in any other Holy Grail Wars. What you see is not possible to be summoned by your Master while I am here.” A transient Servant, the vessel of the Lesser Grail now temporarily manifested in a form resembling one. If the boy did not know of her, then any alternative universe versions of her did not exist either, making her current one the only one.
“May you find your way back to your own timeline soon.” Effectively cutting the conversation there, she raised the cup back to her face for another sip of her drink.