Tsukuyomi operates as a kami within the Department of Custody's Group 1, an organization dedicated to locating, securing, controlling, sealing, or eliminating objects and entities posing potential threats to societal stability. This duty includes retrieving escaped hazards like Byakki.

Physically, Tsukuyomi presents with blonde hair often secured in a ponytail, blue eyes, and a teenage appearance. The character wears a coat and pants. Reflecting mythological roots, Tsukuyomi possesses no defined gender within the series.

Collaboration defines Tsukuyomi's work, primarily partnering with Bekira, a bokor who employs magic-based therapies for spiritual afflictions and manages Tsukuyomi's unspecified condition. Their teamwork extends to field operations, such as pursuing Byakki.

A prior association exists between Tsukuyomi and the fox deity Kūgen Tenko, though the exact nature of their history remains undisclosed. Their paths cross during missions, notably when confronting Momiji Miyabe after her transformation into a lycanthrope capable of controlling others through bites. During this incident, Bekira administers a cure to Miyabe, with Tsukuyomi's actions implied as part of the departmental mandate to neutralize such threats.

The character's background, development beyond the anime's events, and involvement in other media adaptations are not documented.