[@sakurasan]Since they never talked about it in the anime, I'm sorta just amking this up as I go along :lol

But from what I think happens is that Gospel is basically whispering in their heads to prepare to be transported when he wants them to come to him. In the times where they want to go to him, he can just basically let them in at his own discretion.

As for the summoning, I think I'll go with "they're all pulled from space-time" route where they may have just shut their eyes for a second or they might actually have been sleeping, but when they open their eyes up again, they're back in the real world. 

Hope that helps ^^

Also, thanks for the kawaii af pic :D