I've just finished Route B of NieR Automata. During the final cutscene, the ghostly figures of two girls can be seen standing either side of 2B and 9S while
2B strangles the corrupted 9S to death.
I have no idea who or what they're supposed to be, and I'm pretty sure they weren't there when the scene was shown the first time round, during Route A.
Who, or what, are they? Is this something that gets explained in a later route?