Actually, this film is pretty short on answers. Perhaps the manga it is based on has more detail about the hows and whys, but the film remains tight-lipped as to any possible explanations.
This is not a bad thing, though. The film is not about good versus bad, more like A versus B. In the second film, the story introduces the idea that the people we have been following may not be the protectors of humanity at all. Are the aliens really the aggressors, or Gantz and his followers? It hardly matters, because by now enough blood has been spilt (or splashed dramatically against walls) that there’s no chance of forgiveness.
Instead we are thrown into an hour-long fight scene that only pauses long enough for people to get their breath back. While I’m no expert of Japanese action movies, it’s the most physical and kinetic film I’ve seen since Versus. Beautifully acted, shot and choreographed, it carries you along with all the momentum of a roundhouse kick to the face.
The ending is good and wraps everything up neatly. While I think it’s perhaps a little idealistic, it is at least in keeping with the rest of the film. For what it is – a blistering action movie with occasional hints at something deeper – it’s difficult to fault.