In the year 1937 on the eve of World War II, Lieutenant Colonel Yuuki of the Imperial Japanese Army forms the D Agency, an army intelligence outfit under his command and tutelage. Army General Staff attaches Lieutenant Sakuma to observe the unit's performance. D Agency casts a wide net to find agents beyond Japanese military personnel, and Yuuki establishes D Agency's tenets, which go against IJA doctrine: "Don't kill, don't get killed, don't get captured". With this, Yuuki trains a team of operatives who conduct missions against domestic and foreign powers.