The First Investigation Division of the Metropolitan Police Department, which is based in the Dai-Tokyo Police Station , is headed by Keiichiro Funakoshi, the Chief of the First Investigation Division . This is a department that specializes in considerations that lead to solutions.

Along with Ryu Fujii , a new detective who was newly assigned for some reason , they lead to the solution of many difficult cases one after another while colliding with each other's strengths.