Spoiler for Not-the-full-Chapter-21-Spoilers:
Turns out that Jubey was the Pleaides' creation (I think this was obvious at a certain point). Nico fabricated an artificial incubator- which led to becoming Jubey that was under the Pleaides' controls.
That barrier thing above Asunaro City was a spell casted by Umika to make the Kyubey/Incubators imperceptible to the others, then make them remember Jubey- well, replaced Kyubey with Jubey in their memories.
Then they had to simply rely on Jubey to cleanse their Soul Gems instead of using Grief Seeds.. Pretty much screwed up some people.
Some spoilers found so far, at least..
