Sixteen-year-old Yukito Kirihara loves his younger sister, Sana, more than anything in the world. His devotion is tested when an ogre suddenly appears at his window, intending to kidnap Sana. Yukito bravely intervenes to rescue her, sacrificing his own life in the process. Just before his death, a mysterious woman grants him the chance to be reborn, presenting him with a character sheet from a strange book. After spotting Sana's name in the same book, Yukito resolves to find and protect her, even though he begins his new life with only 1 HP.
