Struggling manga author Satoru Fujinuma is beset by his fear to express himself. However, he has a supernatural ability of being forced to prevent deaths and catastrophes by being sent back in time before the incident occurred, repeating time until the accident is prevented. One day, he gets involved in an accident that has him framed as a murderer. Desperate to save the victim, he sends himself back in time only to find himself as a grade-schooler one month before fellow classmate Kayo Hinazuki went missing. Satoru now embarks on a new quest: to save Kayo and solve the mystery behind her disappearance.

Detective Kenichi Itami from the The National Police Agency and Akira Iwatsuki from the cyber investigation team investigate a complex murder case. The victim was under investigation by the cyber investigation team. As Detective Kenichi Itami and Akira Iwatsuki delve deeper into the case, pressure from around makes their investigation even more difficult. Secretly, a national financial doomsday scenario is carried out under the plan of "X Day".