Former diplomat Kiichiro Shirahata is suspected to have illegally gained knowledge of the Imperial Army's top-secret "Grand Strategy." Investigating in secret, Jirou Gamou makes contact with Shirahata's old friend, the British consul Ernest Graham.

Karl Schneider, writer for the Berlin Allgemeine, is suspected of being a German/Soviet double agent. While D-Agency searches for proof of his espionage activities, Schneider suddenly dies under mysterious circumstances. Lieutenant Colonel Yuuki sends his men on individual missions in order to uncover the truth.