A high school student, Subaru Natsuki, is suddenly summoned to another world while returning home from a convenience store. Instead of a summoning ceremony, he's immediately attacked by thugs and faces a life-threatening situation. Rescued by a mysterious silver-haired girl and a cat spirit, Subaru volunteers to help the girl find something in return for their kindness. However, after finding a clue, Subaru and the girl are attacked and killed. But instead of death, Subaru finds himself back where he first arrived in this new world. He discovers he has the ability of 'death return,' where time rewinds to the moment he was first summoned after he dies. Through countless despairs, he struggles to survive...