Since the alien Gitai invaded the Earth, the humankind has been retreating. Now that Japan is almost surrounded by the Gitai, Keiji Kiriya is just one of many new recruits forced into a suit of battle armor and sent out to kill aliens. On a joint mission with the US special force led by Rita, known as the Bitch of the War, Keiji dies on the battlefield, only to find himself reborn.

After 4 times of "death," Kiriya realizes that he has to win the battle to get out of the loop...

Raws
http://tonarinoyj.jp/manga/all_you_need_is_kill/