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Description
Kozue is introduced as a government ninja assigned to accompany Azumi and Nagara on their mission to assassinate Sanada Masayuki. Her outward demeanor is helpful and agreeable, and she quickly earns a place within the group by appearing loyal and cooperative. As the journey progresses, her true intentions remain concealed: she is secretly a spy for the Uenokagashu ninja clan, serving the very forces Azumi and Nagara seek to eliminate.

Her personality is duplicitous. She presents a lighthearted, persuasive front, particularly when interacting with Nagara. She gradually convinces him that Azumi is losing her resolve, that the mission brings only suffering, and that a peaceful life together is a more desirable path. This manipulation is deliberate and calculated, designed to fracture the group and render her targets vulnerable.

Kozue’s primary motivation is to carry out the interests of the Uenokagashu clan and Sanada’s faction. She acts as an infiltrator, using psychological tactics rather than open confrontation to weaken Azumi’s allies. Her role in the story is that of a hidden antagonist whose betrayal triggers a critical turning point, exposing the dangers lurking within trusted circles.

Her key relationships revolve around Nagara and Azumi. With Nagara, she cultivates a false intimacy, allowing him to develop feelings for her while she covertly learns his techniques. Once they are alone, she reveals her true identity and kills him using the very skills he shared with her. This betrayal demonstrates her cold pragmatism. With Azumi, she maintains a pretense of camaraderie after the murder, claiming she and Nagara became separated. When she later attempts to kill Gessai and Azumi intercepts her, the two fight, and Kozue is killed by Azumi. There is no portrayed development or redemption; she remains consistently deceptive until her end.

As a ninja operative, Kozue possesses notable abilities in stealth, espionage, and hand-to-hand combat. She is skilled enough to lethally surprise a trained assassin like Nagara and to engage Azumi in a sword fight. Her greatest weapon, however, is her talent for manipulation, which she uses to sow doubt and division among enemies before revealing her blade.