Suzuna Kuraki trains as the future priestess of her wealthy family's Shinto shrine, a matrilineal legacy requiring consecration rituals and an arranged marriage. This path culminates in the decadal Tsukimachi ceremony, an esoteric ritual welcoming a new clergywoman. Initially aristocratic, conceited, and fastidious, especially toward outsiders, this demeanor masks profound apprehension and solicitousness, making her the household's most anxious member. Her obligation is marriage to subconsciously chosen fiancé Koichi Hayama. Their relationship begins combatively, marked by hostility; Suzuna frequently ejects him from her room as a pervert, though she acknowledges his physical appeal.

A mysterious paranormal energy seeping into the Kuraki estate triggers significant evolution in Suzuna. This force twists her actions and emotions, manifesting in erratic behavior, involuntary sexual encounters, and emotional volatility. Her feelings for Koichi shift dramatically from disdain to intense romantic attachment, culminating in complete devotion. This transformation intertwines with supernatural forces, particularly during the Tsukimachi ceremony, where external manipulations exacerbate her psychological and physical experiences.

Suzuna possesses a monozygotic twin, Mizuna Kuraki, originally destined for the priestess role but displaced after Suzuna's birth. Mizuna resides silently in water caverns beneath the mansion; their relationship remains unexplored. Their mother, Yuriko Kuraki, serves as the powerful family matriarch, significantly influencing household dynamics and the paranormal activities, further complicating Suzuna's journey.

Suzuna shares a close, complex dynamic with childhood friend and maidservant, Tomomi Harukawa. Though Suzuna acts as Tomomi's foil, the supernatural energy influences moments of intimacy between them. Unresolved paranormal mysteries and familial conflicts—especially those involving Yuriko and the displaced Mizuna—leave Suzuna's ultimate fate and story resolution ambiguous.