On the eve of World War II, an international Asian city becomes a hub of a high-stakes “spy game” as spies from countries such as Japan, the UK, the Soviet Union, and Germany compete to give their respective countries any possible advantage in world diplomacy. 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.