Ryuuso no Hana no Monogatari Gin no Himegoto-chou

Ginka, a beautiful and carefree lady-in-waiting, harbors a secret. She is a member of "Tenshoku," a spy organization directly under the Queen. Ginka, cold and calculating yet possessing exceptional interpersonal skills, is assigned a new mission: A long-term assignment to become the wife of a general in the suzerain state and go into hiding abroad. After bidding farewell to her homeland, Ginka meets Tousei, a man of rough but gentle nature. Ginka, who harbors no romantic feelings, calmly fulfills her role as "wife," but Tousei unexpectedly becomes obsessed with her…? (Source: Kadokawa, translated)