>>716361108Shuttah near Nowhere talks about how it's possible to travel between dark worlds. There's also the question of how Ralsei has been able to do so, when chapter 2 clearly spells out that he's not an object that Kris or Susie is bringing with them like Lancer, Roulxs, and Starwalker were.
It's so foggy near the door that it's impossible to see anything, Susie is just stumbling around blind until you catch up and go through the door together.
And of course, whoever Susie sees is so far away that Susie can't positively identify them, she can only make assumptions, and we know Susie is laser focused with a blind spot for extra information that she didn't consider, like there being another person involved.