Well how the person who is gathering us together, let's call the person 'the boss', manages to track him down will be told soon enough in roleplay. As for how he could manage to track the letter down and find out who the person is from an anonymous source from an unknown location is going to be extremely hard so especially with the clear wealth that this person has. he'd have to go along with the second option but he may get suspicious about the other two quincy on the private jet let alone who the humans, fullbringers in actuality, are there for. 

As for trying to work against them that'd...end up pretty badly once the boss catches onto it or if the other players even tells that he may be doing so to the boss isn't very forgiving person. It is ok not to agree with what they're doing and disagree with how the group operates but the purpose at the end of the day is to hunt hollows. If you'd like to know more I'll send you a pm explaining to you why the boss knows about the process but doesn't agree with it.