Gantz:O

Death does not have to be the end; one can live again, but only through beating the game posed by the black ball called Gantz. On his way home to celebrate his younger brother's birthday, brave and kind-hearted student named Masaru Katou is stabbed to death. He awakes in a small room with a cityscape view in the heart of Tokyo—and he is not alone. To his surprise, it is not the afterlife, but the…