Satoru Fujinuma, a struggling manga artist in his late 20s, possesses an unusual ability called "Revival," which sends him back in time moments before a life-threatening incident occurs, allowing him to prevent it. After being wrongfully accused of a crime, Satoru is sent back 18 years to his childhood in 1988. This time leap coincides with a series of kidnappings and murders that occurred during his elementary school years, including the death of his classmate Kayo Hinazuki. Realizing that his return to the past presents an opportunity to alter these tragic events, Satoru resolves to save Kayo and uncover the identity of the killer.

As a child, Satoru reconnects with Kayo, a lonely and abused girl who becomes the primary target of the kidnapper. Through his efforts, Satoru forms bonds with Kayo and other classmates, including Kenya Kobayashi, a perceptive and intelligent boy who becomes an ally in Satoru's mission. Satoru's actions gradually change the course of events, but the killer remains elusive, and the stakes grow higher as more children are threatened. The narrative intertwines Satoru's childhood experiences with his adult life, revealing how his actions in the past ripple into the future.

The story delves into themes of trauma, redemption, and the consequences of one's choices. Satoru's journey is marked by his determination to protect those around him, even as he grapples with the moral complexities of altering the past. The identity of the killer is revealed through a series of twists, connecting the past and present in unexpected ways. The resolution of the story ties together the timelines, showing how Satoru's efforts ultimately reshape his life and the lives of those he sought to save. The narrative maintains a balance between mystery, emotional depth, and the exploration of human resilience in the face of tragedy.