Arnée Brillhit is the Western Empire's hero and most skilled swordmaster, dedicated to serving her nation. But in the eyes of her mother, Arnée is first and foremost a distinguished duke's daughter, who—though exceptionally beautiful—is still unmarried. Her mother only wishes for the free-spirited daughter to find true happiness by falling in love and being loved.

When Grand Duke Cassian Ternuzen of the Northern Empire comes to select a bride from the Western Empire, Arnée's unique personality leaves an impression, and he asks for her hand. Although Arnée has no desire to wed, her mother begs her to endure for a mere three months, after which she may divorce and return home if she completely dislikes married life. Fearing that Cassian would reject a knight, Arnée keeps her occupation a secret and acts as a frail and gentle lady—but Cassian's attention and coddling might not be so unwelcome after all.