To the anon asking abt the novel with assassin plot. Well my recommendation doesn't exactly fit your story, still you can try it . So there is a manhwa where the empress of a nation disguises herself and becomes the concubine of enemy emperor to assassinate him. It's called "the emperor 's concubine". What i find interesting is that the female lead is brave , smart and very consistent. Even when the emperor showers her with love and favor everyday, not once she deviated from her goal.