Kō stands guard as the Mizuchi family's sentinel, tasked with monitoring and protecting the Takagami brothers, Noboru and Tōru, alongside the fox deity Kugen Tenko. This duty requires her residence within the Takagami household. Her primary focus remains surveillance and safeguarding the brothers from supernatural threats, especially those drawn to Tōru's spiritually attractive Yin bloodline.

Trained as a shrine maiden, Kō exhibits unwavering dedication to her duties but displays significant unfamiliarity with modern human customs and domestic chores. Her attempts to help often accidentally destroy household items, such as wearing holes through steel pans while washing. This clumsiness stems from an upbringing centered solely on combat and spiritual discipline. Socially inexperienced, she communicates in a unique manner, frequently resorting to mimicking actions or sounds to express herself, perceived as peculiar despite her serious nature.

A defining aspect of Kō's existence is the dragon spirit Rinsenmon residing within her body; the circumstances of its possession remain unexplained. Periodically, this internal dragon manifests physically, causing emerald scale-like patterns to bloom across her skin. She consistently wears her shrine maiden attire, reflecting her traditional background and role.

In combat, Kō specializes in water-based magic for both offense and support, skills honed for spiritual battles rather than practical tasks. Over time, she shows incremental improvement in basic household activities, such as successfully cooking rice, though complex chores remain challenging.

Her relationships within the household involve a formally protective dynamic with the Takagami brothers, whom she addresses with the honorific "sama." Hints of deeper feelings for Noboru add complexity to her professional duties. Interactions with Kugen Tenko involve shared protective responsibilities, though friction arises from Kō's solemnity clashing with Kugen's mischief.