This question been bugging me, I mean are they trying to take over Earth. I mean, I remember the green onion alien with it father and son, they just trying to survive. The aliens didn't do anything that suggested invasion they like illegal Immigrant coming over to america to survive not invade. I mean if they were here before Kei was a gantz hunter then why didn't they try to overtake Earth yet.
Are they a threat? If so Why?