Here's a few interesting insights I found during my search. During the fight between Gil and Arthur everyone was evacuated, not a single soul was around. This could be a doing of a marble phantasm, however, this image here proves that the battle is collapsing to the real world and everyone is witnessing it.
https://i.imgur.com/90KnAoK.jpg
Another key frame here shows that Gil successfully Flooded the whole city and possibly killed millions. Notice the Water kanji and the battered up Ayaka who probably tried to carry Arthur all the way to the roof all by herself.
https://i.imgur.com/jCy9MrT.jpg
The question here is who cast away the civilians during the duel? If Gil's flood did killed everyone, my guess here is that Manaka took the opportunity to consume the poor souls who were washed away and resurrect herself, after all, she can see the future.