Hiroko Takashiro begins her journey as a curious high school student drawn to witchcraft, forming a secretive occult club with classmates. Their discovery of the grimoire *Bible Black* leads to reckless experimentation, including a lust spell that humiliates a student council member. Ambitions spiral into a failed demonic summoning ritual, culminating in her violent assault by the entity they unleash. The trauma fractures her psyche, driving her to renounce dark magic. Over a decade later, she returns to her alma mater as an art teacher, quietly safeguarding the sealed basement housing her group’s occult remnants. Haunted by imagery tied to her assault, she experiences involuntary arousal that culminates in a coerced encounter with a possessed vice-principal. Drawn into confronting Reika Kitami—a vengeful former sacrifice orchestrating soul-transfer rituals—she allies with student Taki Minase, reclaiming the *Bible Black* grimoire to dismantle Kitami’s schemes. Throughout, she endures repeated sexual exploitation and brutality while resisting dark forces. Seeking redemption, she retreats into a monastic life, adopting nun’s attire to suppress lingering temptations. Yet she persists in combating occult threats, including Kitami’s resurgence in a new host. Utilizing white magic and religious texts, she neutralizes dangers, ultimately imprisoning Kitami’s soul and purging traumatic memories from survivors. Side narratives expose unresolved vulnerabilities: repressed fantasies about students, a trauma-induced relapse with the vice-principal in a faculty restroom, and conflicted urges beneath her composed facade. These moments underscore the enduring grip of her past. Her evolving appearance mirrors inner turmoil. As a student, she dons uniforms and ritual robes; as a teacher, formal attire with signature stockings; later, modest nun’s garb and a kimono signal spiritual transformation. Hairstyles shift from youthful red mid-length locks to adult-long waves, then cropped beneath a nun’s hood. Relationships intertwine mentorship, rivalry, and fragility. She guides Minase against Kitami while navigating tensions with former coven allies. A post-trauma entanglement with Minase merges tactical alliance and emotional dependency. Her final role as a maternal figure and mentor highlights a guarded, celibate resolve—a fragile shield against unvanquished shadows.