Gantz Perfect Answer (English subs)

Kei Kurono (Kazunari Ninomiya) and Masaru Kato (Kenichi Matsuyama) are summoned by the mysterious black globe GANTZ. They continue the fight against extraterrestrial beings and, as they continue to battle, they become stronger. They can't escape unless they kill their enemy, the Saint.
Kei Kurono opts to keep fighting to survive, but Masaru Kato hates the world which is controlled by violence and refuses to fight. As the two friends finds themselves opposing each other in a continuous game of violence, a critical last choice is to be made.