"All You Need Is Kill" is a science fiction light novel written by Hiroshi Sakurazaka. The story follows Keiji Kiriya, a soldier fighting against alien invaders known as Mimics. After dying in battle, he discovers he has the ability to reset time, reliving the same day over and over. As Keiji learns to navigate this cycle, he teams up with a skilled warrior named Rita Vrataski, who has also experienced similar time loops. Together, they strategize to defeat the Mimics and find a way to break the cycle, leading to intense action and character development throughout the narrative.