okay, why is Eirin in there?

B016 said:

okay, why is Eirin in there?

Some theories about Sakuya's origin conects her past with the Lunarians (By Hieda no Akyuu in Perfect Memento in Strict Sense). So, you can play a lot with those lines and theories.

There's also the fact that, for some reason, Eirin was surprised to see Sakuya in Imperishable Night.

regarding the plot, I'm going to say Flan is out of the fight because she's never had to endure actual damage, Remi, on the other hand, is going to get knifed and she won't even flinch and *then* will slap pre-sakuya here into utmost servitude.

Kind of shaky translation added.