Wow this is a very interesting chapter, Phantom Thief G seems like a cool character to introduce. For some reason I think its an innocence with a physical form or a person with an innocence but they can't control it because it has its own will. (or the person can and their just childish lol) Whoever this Phantom Thief G is I'm curious about them, I wonder who he'll possess next. Allen? I hope not, to much character develop from him already but it could work. Kanda? Maybe, could be the person he's looking for since this guy has been running a mock for over half a year it could have been longer. Marie? Could work, he hasn't had much development at all but tis is the suffrage of being a minor character.
Hopefully the Order gets a new member of the team by this arc's end. They can't be an akuma, no killings yet, no noah either for the same reason. Its probably human, some type atleast.
But yeah, a phantom innocence that can possess others and possibly do more will be really intersting.