Hiiragi, a recurring youkai, first emerges as a target of exorcism by Shuuichi Natori. Their bond begins in childhood when he treats her injured hand with unexpected kindness, sparking an enduring attachment. Despite Natori’s later attempt to exorcise her, this connection evolves, culminating in her voluntary role as his third shiki—a testament to their complex history.

She possesses short pale blonde hair and piercing blue eyes, her face obscured by a horned mask adorned with a prominent central eye. A jagged crack splits the mask, a remnant of Natori’s failed exorcism. The mask shatters entirely during a confrontation that ruptures the priest’s bindings confining her to a shed, freeing her to choose her own path beside Natori.

Blunt and unflinching, Hiiragi voices her opinions with little regard for tact, often clashing with others like Takashi Natsume when her boundaries are challenged. Yet her loyalty to Natori remains absolute, forged through years of shared trials. Though initially dismissive of Natsume, she gradually acknowledges their parallel struggles with isolation and human ties, fostering a cautious rapport.

Originally hailing from a mountain home, Hiiragi was forcibly tethered to guard a shed under a priest’s command, her will suppressed until Natori’s exorcism inadvertently breaks her chains. Her choice to become his shiki defies conventional spirit contracts, driven by gratitude and lingering ties rather than obligation. The name "Hiiragi," meaning holly, mirrors her resilience and protective nature, echoing the endurance that defines her journey.