Detective Yamazaki investigated the disappearances of twelve children in Matsada twelve years before the main events, leading to the capture of Ichinose—an unstable young woman convicted of kidnapping based on circumstantial evidence, though no murders were proven. After Ichinose vanished, Yamazaki remained haunted by the unsolved case, carrying photographs of the missing children in his wallet and refusing to close the investigation despite its official status. Twelve years later, the children’s skeletons were discovered at a Hadoka hotel construction site alongside evidence linking the now-deceased Ichinose to the crimes. This prompted Yamazaki to enlist necromancer Misaki Saiki’s assistance during her vacation, seeking conclusive evidence to resolve the case and bring peace to his troubled mind.