- When police officer Saegusa Kento was a child, a girl who was his friend was kidnapped and murdered. He witnessed a mysterious woman take her away. Although he told the police what he saw, he was ignored by everyone. The case has remained unsolved for 15 years and the statue of limitation is approaching. One day, Kento hears a voice from a walkie-talkie which was supposed to have been disposed. The speaker Oyama Takeshi says he is a detective pursuing the same case as Kento and he has a lead related to it. At first, Kento finds it hard to believe. But when he heads to the location that the detective told him about, he discovers a skeleton down there. After that, he continues to communicate with that detective. He learns that the man is someone living in the past. The two of them begin to work together to crack unsolved cases through the mysterious walkie-talkie.