Who said that the D-agency is only composed of spies? Peacetime has passed away and the countries have declared war. The secrets of the past are yet to be revealed and the fate of the future remains a mystery. It was, critically, stated that spies are only reliable during the quiet days and are no longer of use during the time of war. If such opinion was indeed proven, the D-agency will be forced to suspend and all the duties of the spies will be given a halt. However, Colonel Yuuki still has another or final card rather, underneath his sleeves-- The final card that can save the existence of the D-agency along with its remaining spies. And you know what made such decision much more surprising? It's a girl; a lady.

As the embers of World War II smoldered in autumn of 1937, Homare Sasaki was aware of the number of men constantly being summoned to battle. And the likely amount of them who might not make it through the war later. Yet it doesn't stop her from taking a scalpel into a patient's body, saving lives rather than taking a knife into someone's heart for the sake of her survival. When Sasaki uncovered a stolen intel left behind by her dead father, she knows she could trust no one anymore if she wants to hold on to her dear life. Then a handsome stranger breaks into her house at the middle of the night, just to give her a kiss before knocking her unconscious. She decides to trust Sakuma the soldier and follows him to the Greater East Asia Cultural Society for protection. All without knowing the clandestine spy agency operating under its name...