Satoru Fujinuma is a struggling manga artist working at a pizza parlour. Ever since he was a kid, he has been holding himself responsible for a kidnapping incident and finally the time has come for the truth from his past to be revealed.

After Satoru discovers his mother brutally murdered in his apartment, he goes back 18 years in time, before classmate Kayo's kidnapping and murder.

As Satoru relives his childhood days at school, he befriends Kayo and stays by her side on March 1 to thwart the kidnapping that would take her life.

Unsure if Kayo is alive, a distraught Satoru is suddenly transported to the present, where he is a suspect in his mother's murder.

Satoru meets Sawada, a former colleague of his mother, who is also looking for a link between her murder and the kidnappings from the past.

Kayo shows her friends the bag an angry stranger hid inside the bus. Inspired by Satoru, his mother and teacher take action in order to help Kayo.