From Wikipedia:
Subaru Natsuki is a NEET who is suddenly summoned to a fantasy-like world. Just after arriving, he is killed while trying to help a young elf he befriends, Emilia, who is a candidate to become the next ruler of the Kingdom of Lugunica, only to revive some hours in the past. After dying some times, Subaru realizes that he has the power to turn back time after his death. After successfully helping Emilia, Subaru starts living in her house as a butler. Out of gratitude and affection for Emilia, Subaru makes use of his newfound ability to protect her and help on her ambition to be successfully appointed as the next queen, also providing assistance to other friends he makes along the way, while suffering due to the pain inflicted on him every time he dies, and carrying along the memories of everything that happened before his power activates, which is forgotten by everybody except for him.
