Police Precinct: Backing Investigation

The story

A man confessed to killing a woman in a labyrinth 2 years ago. The detectives must now conduct a "backing investigation" to determine whether his confession is true, because the law states that a confession alone is not enough to make the case. The 20nd work from the popular series "Keishicho Monogatari", which documents the activities of the First Investigation Division of the Capital Police Department.