A and B have ended up in past, but maybe sure yet, although they have seen people that look like the younger versions of people they know. We pick back up with them with A saying this and B responding.
A: B。 やっぱりここって過去の世界？
What's confusing for me is the entire やっぱりここって construction. って is most obvious the quoting bit. With ここ I guess it's saying that here/now is the past. A is wondering if they really are in the past. What does やっぱり then do? This is my current tentative translation.
A: B. You still think we are in the past?
B: Ughh…we might have no other choice but to assume that…