Hallway (prison)

The hallway is the main area of the prison, connected to four prison cells and two workrooms. One of the cells belongs to Shūji Orinaka, a former boxer. A hole on the floor of Orinaka's cell led to a tunnel connected to a well in the prison courtyard.

The Supplier
When assassin Ryōken Hōinbō was arrested and sent to prison, he blackmailed the warden, Marī Miwa, into cooperating with him to smuggle various goods into the prison for the benefit of the inmates. Every month, Miwa would drop the items down the courtyard well, and Hōinbō's dog Kuro would take them through the tunnel to Hōinbō's special cell.

Orinaka's escape attempts

 * Main article: The Imprisoned Turnabout

Over a period of weeks in 2019, Orinaka extended the tunnel connected to his cell using tools supplied to him by Hōinbō, in hopes of escaping. His tunnel extension eventually made it to the detention center's holding cell. In March, Manosuke Naitō was arrested and sent to the holding cell. Seeing his chance, Orinaka attacked Naitō and his guard escort as he was being locked up, and stole the keys to the holding cell. He then returned to his own cell so that Naitō would be blamed for stealing the keys, and waited for an opportunity to make his break.