Alice and Byakuren went to visit Shinki and brought tons of friends along with them?

I'd say they all went to meet old friends. Mai is wondering who is Alice, Marisa is pranking similar-looking Yuki, Flan plays with Socrates, Byakuren talks to Rikako... slice of life.

Sulejman said:
Mai is wondering who is Alice

Alice must've changed a lot for Mai to no longer recognize her if that's the case.

game2009 said:

Alice must've changed a lot for Mai to no longer recognize her if that's the case.

Growing up and getting a species change will do that.

game2009 said:

Alice must've changed a lot for Mai to no longer recognize her if that's the case.

Or maybe she's just stunned as to how much she's changed.

Sulejman said:

Flan plays with Socrates

Well, that's one way to put it! A nice image whatever the background may be.