Given the presence of Command Spells on the back of her right hand, another War is definitely a possibility. Not actually the case, but definitely a reasonable conclusion to come to. For her part, though, Ritsuka looks both a little surprised and a little chagrined. Since she's arrived, only Servants from Chaldea have shown up here, so she's gotten just a bit too used to knowing everyone. In any case, she gives the Lancer an apologetic smile.

"Sorry, I guess I know a different version of you." A couple of them, in fact. "My name's Ritsuka. Ritsuka Fujimaru. I'm from Chaldea."

If he doesn't recognize her, there's a good chance he won't recognize Chaldea, either, but it doesn't hurt to mention, right?