Fujinuma Satoru (voiced by Manshima Shinosuke) has the special ability to go back to the past. His mother Sachiko (voiced by Takayama Minami) was killed, and his once trusted friend Shiratori Jun (voiced by Mizushima Daisuke) was about to be sentenced to death as the real murderer of the child serial murder case. At this juncture, Satoru suddenly returned to 1988 and returned to the elementary school he attended at that time. At that time, his classmates Hinazuki Kayo (voiced by Yuuki Aoi) and Yamada Hiromi (voiced by Kito Akari) who died in the murder case had not yet been killed. Satoru was determined to use his ability to protect the safety of Kayo and Hiromi, wash away the grievances of Shiratori Jun, and find the real mastermind behind the scenes. With Satoru's efforts, Kayo, who has a gloomy and withdrawn personality, finally opened her heart to him, and the two formed a deep friendship. Soon, the day of the case came, the vast night passed, and when the light came, could Satoru see Kayo's innocent smile again?