The First Investigative Division is the star unit of the Tokyo Metropolitan Police Department. Jun'ichi Ōiwa, the head of the division, leads around 400 elite detectives. He has an extremely heavy responsibility: attends initial investigations at the scenes of all brutal crimes that occur within the metropolis, decides on the course of action of the investigations at the same time as he directs many investigation task forces and gets into investigations himself at the critical phase. However, Ōiwa is definitely not a superman. Amid his suffering, Ōiwa overcomes this grave responsibility and is quite simply a "life-size hero" and "ideal boss" to his subordinates.

• Takashi Naito
• Yuki Saito
• Hirotaro Honda
• Akio Kaneda
• Hiroki Suzuki
• Hana Hizuki
• Nobuyuki Hanawa
• Hiroki Iijima