Subaru Natsuki, an ordinary teenager, is suddenly transported to a fantasy world while returning from a convenience store. Upon arrival, he discovers he possesses no special abilities, unlike typical protagonists in such settings. Shortly after, he encounters Emilia, a half-elf girl searching for a stolen insignia, and her spirit companion, Puck. Subaru decides to assist her, forming a bond that becomes central to the narrative. However, Subaru soon realizes he has a unique power: "Return by Death," which allows him to return to a specific point in time upon dying. This ability comes at a cost, as he retains the memories and emotional trauma of each death, while others remain unaware of the loops.

The story unfolds across multiple arcs, each exploring Subaru's struggles as he navigates the complexities of the fantasy world. In the first arc, Subaru becomes entangled in a conspiracy involving the insignia theft and the assassination of Emilia, leading to repeated deaths and resets as he attempts to alter the outcome. His determination to protect Emilia drives much of the narrative, even as his mental and emotional resilience is tested. The second arc shifts focus to the Roswaal Mansion, where Subaru works as a servant alongside maids Rem and Ram. Here, he faces mysterious threats, including a curse and an unseen assailant, forcing him to rely on his ability to uncover the truth and save those around him.

Key characters include Emilia, a kind-hearted yet misunderstood candidate in the royal selection to become the next ruler of the Kingdom of Lugnica; Rem and Ram, twin maids with contrasting personalities and hidden depths; and Roswaal L. Mathers, a powerful mage and Emilia's sponsor, whose motives remain enigmatic. Subaru's relationships with these characters evolve significantly, particularly with Rem, who becomes a steadfast ally and source of emotional support. The royal selection introduces other candidates, such as the ambitious Crusch Karsten and the ruthless Priscilla Barielle, adding political intrigue to the story.

The narrative delves into themes of perseverance, self-sacrifice, and the psychological toll of repeated failure. Subaru's journey is marked by moments of triumph and despair, as he grapples with the consequences of his actions and the limitations of his power. The series balances intense emotional moments with action, mystery, and world-building, creating a layered and engaging story. The fantasy world is richly detailed, with its own history, magic system, and societal structures, providing a compelling backdrop for Subaru's trials. Through its intricate plot and character development, "Re:ZERO -Starting Life in Another World-" offers a unique take on the isekai genre, blending fantasy, drama, and psychological elements.