Twelve years prior, Detective Yamazaki was involved in solving the disappearances of twelve children in Matsuda, all of which had not been found. His efforts led to the capture of an unstable young woman, Ichinose. Through circumstantial evidence, Ichinose was convicted of the kidnappings but not any murders. Ichinose later disappeared herself.

In the interim, Yamazaki continued to try to prove that Ichinose had murdered the twelve Matsuda children. However, the case had long since closed, but the haunted Yamizaki refuses to let the case go, keeping the pictures of the children in his wallet. Now twelve years later, the skeletons of twelve children, along with evidence which tied the now-deceased Ichinose, was uncovered by chance at the construction site of a hotel in Hadoka. Yamazaki is pressed to enlist Misaki Saiki, who was on vacation at the time, to help him find the evidence that would at last ease his troubled mind.

(source: Absolute Anime)