Homura operates as a karas, an agent appointed by an unnamed city to execute its will and enforce equilibrium among humans and yōkai. Her specific city of origin remains unidentified.

Her involvement centers on the Shinjuku conflict. She intervenes to save Otoha, Tokyo's newly appointed karas, from yakuza assailants. Later, alongside fellow karas, she witnesses the climactic battle between Otoha and Eko, the rogue former karas of Shinjuku. When Eko merges with a powerful entity, Homura joins the final confrontation to aid Otoha.

Homura possesses the standard abilities of a karas. She can transform into multiple forms, including an armored warrior, an automobile, and an aircraft. Her combat skills feature swordsmanship, consistent with other karas agents. Like all karas, her power derives from Yurine, the physical manifestation of a city's will, involving the infusion of a human soul into karas armor through Yurine's recitation of a Shinto prayer.