In case you can’t tell, the not-yet-introduced person in question is Rip van Winkle, vampire in the service of Millennium.
Fangirl: But doesn’t everybody know about [censored]?
Fangirl: Yeah: she is in the manga, after all.
Erin: Uh-huh. But in this timeline she hasn’t shown up yet. Most fangirls have heard of [censored] but the characters haven’t.
Besides, it would be too easy to have the fangirls, who are pretty much omniscient, tell them about [censored]…
Seras: Master, what are they talking about?
Alucard: I have no idea.