Koume is the close companion of Hinazuru, the geisha identity of Sumie Kanomata. She possesses no knowledge of Hinazuru's hidden past as a survivor of wartime atrocities or her covert mission against responsible figures in the Meiji government, remaining unaware of Hinazuru's motivations and actions. Koume's own history before meeting Hinazuru is undefined. This friendship places Koume in grave peril during an incident involving Zenbei Kuraya, the former samurai Masaomi Kuramoto. Kuraya leads a violent "hunting club" that targets women for nocturnal killings, and Koume becomes one of its intended victims. During the attack, Shizuma Origasa and Hidenobu Osanai, acting without official sanction, intervene upon witnessing Kuraya and his men pursuing her. Their actions, combined with the arrival of police reinforcements, result in the capture of Kuraya's group and Koume's rescue. The immediate threat posed by the hunting club ends when Hinazuru assassinates Kuraya from a distance. Koume's documented role centers entirely on her relationship with Hinazuru and her involvement in this hunting club incident.