You're watching spies outwit each other in 1937 Japan, and every episode resets the board with a new impossible problem. The show doesn't care about giving you a main character or a storyline, it cares about the puzzle, the setup, the moment someone realizes they've already lost. If you want plot momentum, this will frustrate you; if you want to watch humans dismantle each other with nothing but information and nerve, this is the only show doing it at this level.

The year is 1937, and a world war is looming. Within Japan's imperial army, Lieutenant Colonel Yuuki sets up D Agency, a spy unit he commands and trains personally. Its rules break with army doctrine: don't kill, don't die, don't get caught. Lieutenant Sakuma is sent by the General Staff to watch how the unit performs, while Yuuki recruits agents from well beyond the ranks of the Japanese military. His operatives are trained to endure harsh conditions and to master fields such as languages and communications, but their sharpest weapon is the ability to manipulate people. They run missions against powers at home and abroad, gathering the information Japan wants as war approaches. The result is a psychological spy thriller where outsmarting opponents matters more than outgunning them.