Schoolkids Junichi, Makiko, Keisuke and Naoto bury a gun under a tree. Twenty-three years later, Junichi, now a detective, reunites with Makiko.

Nara and Junichi check the supermarket's security footage and call logs. Later, Junichi suggests to his friends that they dig up their time capsule.

Junichi's friends grow testy when they discover the gun is missing from the time capsule. Keisuke convinces Makiko to go to the police.

Nara becomes convinced of a connection between the present and past cases. Junichi learns that Keisuke's car was seen near the burial site.

Nara asks Naoto to come to the police station voluntarily when his alibi crumbles. But questions about the time capsule and the weapon remain.

Shaken by the secret that Naoto has been hiding for 23 years, Junichi faces his own misdeed. Nara asks a new person to come in for questioning.

At the scene of the incident from 23 years earlier, Makiko and Keisuke are shocked to learn what Naoto witnessed. Nara warns them to keep it a secret.

Junichi suspects Naoto is covering for Makiko, but Naoto refuses to retract his confession. Meanwhile, Makiko and her son go missing.

Nara uncovers new facts from the gun. Later, Junichi has a breakthrough when Naoto recounts a key detail from that day 23 years prior.