Nanaka serves as a shopkeeper and secretary for the organization overseeing the Mitsurugi, humanoid swords tasked with combating evil spirits. Known for her kindness and politeness, she assists the protagonist by distributing starter equipment, explaining interface mechanics, and offering guidance. Her responsibilities encompass administrative support, logistics management, and facilitating internal communication.

She shares a close bond with her younger sister Yayoi, a mechanic within the same organization. Their dynamic underscores Nanaka’s nurturing and responsible nature, contrasting Yayoi’s energetic demeanor. In the anime adaptation, Nanaka manages daily operations at the Western-style tea house "Meiji Mansion," where Mitsurugi balance combat duties with civilian life. She ensures seamless coordination between missions and the tea house’s activities, maintaining its role as a social hub.

Nanaka’s interactions with the Mitsurugi and protagonist highlight her reliability and organizational expertise. She provides essential resources such as the sword Ookurikara, currency, and upgrade materials, serving as a foundational support figure. Her consistent presence across both game and anime narratives reinforces her role in sustaining the operational backbone of the Mitsurugi’s efforts, though her background prior to joining the organization remains unaddressed in existing materials.