That's because we've met before. Or... rather, we will. Several hundred years in your future, from the look of you. The name you gave me at that time was Genya Arikado - a localized version of your chosen name, Alucard. But we've also met here before, as well - you as you are now, and me as I am. This place is really, really strange, when it comes to timelines, so I'm not terribly surprised you don't recognize me.

[He folds his arms, returning that same looking-over.] I can make some reasonable guesses, as well. You're wondering why you feel you should know me, even though we've never met before. Am I right?