Lieutenant Andy Shaw is a recently commissioned officer. He is an officer of the United Defense Squad. Despite the deployment of soldiers equipped with powerful exoskeletons, the United Defense Force is losing the war against the mysterious aliens known as Mimics, who have taken over the Earth.
Andy is seemingly killed on his first sortie after killing an abnormal-looking Mimic, but, through some inexplicable event, he awakens to find that he has returned to the day before the war. As this process continues, he finds himself trapped in a time loop as his death and resurrection repeat over and over again. Andy's skill as a soldier grows as he passes through the loop each time he manages to change his fate. After several dozen cycles, he learns that his fate is similar to that of Rebecca, a major ace who preferred to use a battle ax rather than a firearm. He uses his knowledge of the day to get close to her and her mechanic, giving her a copy of his giant axe. He learns to use the weapon well; The boltgun that was issued to most soldiers quickly ran out of ammo and jammed easily.
Realizing that he is a fellow Looper, Rebecca confides in Andy, telling him about the system used by the Mimics: upon death, they have the ability to send a signal into the past, allowing them to see the future. Allowing you to change your behavior to see and avoid it. Luck. In each cluster of mimics, a central nexus serves as the day loop that can cause the loop, as well as several antennae mimics, all of which signal the loop to reset; Andy is caught in a loop after coming in contact with one such antenna. To escape like Rebecca, Keiji must first kill all the antennae and then the Nexus. Mimic constantly adapts to Andy's attacks. He and Rebecca manage to dismantle the nexus, only to reset the loop with Rebecca forgetting what has happened. After telling this to Rebecca, she admits that they missed an antenna. On the 160th loop, they proceed to eliminate the antenna again. Rebecca then attacks Andy when they are out of sight of the allied forces, explaining her hypothesis that being caught in the loop has caused her to change her mind. In essence, both antennae are identical to Mimics, meaning that one of them must die before the Nexus can be killed; Otherwise, the loop will continue indefinitely. Reluctantly, the two fight. Andy mortally wounds Rebecca and remains with her as she dies. As Rebecca dies, Andy confesses his developing feelings for her, before telling her to win the war quickly and prevent anyone else from suffering his fate. He slaughters the remaining mimics and destroys the nexus. Weeks later, he is hailed as a new hero of the Joint Defense Squad, while he quietly reflects on what happened and the sacrifices needed to win the war. He paints his exoskeleton blue in honor of her memory.
