From MangaHelpers:

Aihara Ryouji is a police detective who has been assigned to department 0. In department 0, a uniform is no longer necessary, and their messy headquarters is adorned by a full-length nude female poster. Department 0 handles whatever the main headquarters can't decide what to do with, and their office is packed with old files. Aihara gets to work right away, and becomes involved in a kidnapping case. In the meantime, he's getting to know his few co-workers, and possibly starting a romantic entanglement with an eager female cop. [tethysdust]