Time travel, imaginary world, imitation of the Song Dynasty, army, passwords, tactics, duel, ancient technology, hard-core password warfare.
A modern engineering soldier travels to Xiao Yi in the fictional Jing Dynasty (imitating the Song Dynasty). The protagonist was forced to retire due to military leaks before the time travel, and became a spy for the enemy country after time travel. Watch the protagonist combine modern military knowledge with ancient survival wisdom to crack codes and mechanisms, and the mutual confrontation between spies and counter-espionages.
