Inappropriate timing but Gantz is a very problematic manga but the overarching plot at the end is revealed to revolve around
spoiler
racist aliens that look suspiciously like humans that live in futuristic western-like cities invading Earth with superior technology to steal land, resources, slaughter resisting humans, and herd the surviving humans like cattle for food and amusement
Inappropriate timing but Gantz is a very problematic manga but the overarching plot at the end is revealed to revolve around
spoiler
racist aliens that look suspiciously like humans that live in futuristic western-like cities invading Earth with superior technology to steal land, resources, slaughter resisting humans, and herd the surviving humans like cattle for food and amusement