Subaru's first day at the Roswaal mansion begins for the third time. The first time, he grew weak and died of unknown reasons in his sleep, and the second time, he was killed by an attacker. The sound of chains that he heard as he died the second time replays in his mind, waking him in a terrified, cold sweat. He has no idea what the killer is after, let alone who it is, so he makes a plan to leave the mansion on the fourth night and watch for the attack to happen.

Suddenly, high school student Subaru Natsuki has been summoned to another world on the way back from the convenience store. With the biggest crisis of his life being summoned to another world, and with no sign of the one who summoned him, things become even worse when he is attacked. But when he is saved by a mysterious, silver-haired girl with a fairy cat, Subaru cooperates with her to return the favor. When they finally manage to get a clue, Subaru and the girl are attacked and killed by someone. Subaru then awakens in the place he was summoned and notices he gained the ability "Returns by Death" and has become a helpless boy that only has the ability to rewind time by dying. Beyond the despair, can he save the girl from the fate of death?