All You Need Is Kill

The story is told from the perspective of Keiji Kiriya, a new recruit in the United Defense Force. Despite equipping its soldiers with powered exoskeletons, the UDF is losing its fight against the mysterious "Mimics" (ギタイ, gitai), extraterrestrials who have laid siege to Earth. Keiji is seemingly killed on his first sortie after killing an unusual-looking Mimic but, through some inexplicable phenomenon, he wakes and finds that he has returned to the day before the battle. As this process continues, he finds himself caught in a time loop as his death and resurrection repeat time and time again. Keiji's skill as a soldier grows as he passes through each time loop in a desperate attempt to change his fate. After several dozen loops, he realizes his fate is similar to that of Rita Vrataski, a prominent ace who preferred to use a battle axe rather than a firearm. He uses his knowledge of the day to get close to her and her mechanic, from whom he gets a copy of her massive axe. He learns to use the weapon well; the boltgun that most troops are issued quickly runs out of ammo and jams easily.