Set along a backdrop of a fictitious second world war at an international city in Asia. In Japan, Lieutenant Colonel Yuki recommends the creation of spy training school "D Kikan". Meanwhile, Kato is facing capital punishment for his refusal to follow a superior's order. Kato is then scouted by "D Kikan". He goes through a harsh training regiment and faces his first mission as a spy. In order to seize American ambassador Graham's confidential documents "Black Note", Kato infiltrates into an international city. A battle to gain possession of the "Black Note" ensues between Kato, a mysterious woman named Rin, the British Spy Agency, the Soviet Spy Agency and the radical army in Japan.