This is a Japanese all CGI all-the-time Sci Fi spectacular ... with everything bad that implies. In some very near future, Masaru Kato (voiced, in English, by Kaiji Tang) dies while trying to save someone from a knife attack in the Tokyo subway. He wakes in a room where it's very badly explained to him that dead people are resurrected and have to play a game: they're teleported with weapons to where monsters are attacking cities and they have to survive, make points, and kill all the monsters, all in two hours. The fact that it's in a city centre and normal people die by the hundreds around them is not - initially - a subject of discussion.
The CG humans look like something from a high end video game cut scene. The women are every bit as realistic as - and built like - Lara Croft. The men aren't quite so unrealistic, although they don't exactly look human either. The "acting" (if it can even be called that) is appalling. The character's behaviour is idiotic, even given the bizarre circumstances they're thrown into. It's bloody, violent, nasty, and really silly.
I'm beginning to think that one of the features of manga - this is based on a manga, and I'm not a manga reader so my interpretation is gleaned from other from-a-manga movies - is that the idea of throwing people into a really wild situation and seeing what happens is all that matters ("Attack on Titan" comes to mind). No explanation is given of where the monsters come from. No explanations of the resurrection, teleportation, or weapons technology are given. No explanation is given of why killing the monsters has been gameified, nor why you wouldn't just given the weapons technology (and resurrection and teleportation) to the military, who are actually trained for fighting. So ... this is just about people in a weird situation. I could deal with that if the people were well written. They are not.
In the end, the only redeeming feature for me was the monster design: the Japanese often have a significantly different vision of what "monster" means. A few are so out there they mostly seem silly to North Americans, but most of them are weird and seriously scary. But this sure as hell isn't enough of a reason to watch a movie this bad.