Nagi Kirima was born into a strange and deeply intellectual household, raised by her father Seiichi Kirima, an eccentric and enigmatic author who shaped much of her philosophical and rebellious mindset. Despite not being related by blood, she grew up alongside Masaki Taniguchi, forming a close, protective bond with him. Her circle also includes Naoko Kamikishiro and Kazuko Suema, who recognize both her brilliance and her inner struggles.

From a young age, Nagi exhibited strange powers connected to an inner force later revealed as the Witch of Fire, Walpurgis. This presence nearly destroyed her during her childhood, until it was suppressed through intervention by Shinpei Kuroda, a mysterious agent of the Towa Organization. This trauma—combined with her awareness of the world’s hidden horrors set her on a path of relentless self-discipline, combat training, and philosophical resistance against the unnatural.

Nagi is a tall, athletic young woman with short, spiky dark hair and intense sharp eyes that often convey her unwavering determination. Her signature look includes casual, boyish clothing, such as hoodies, loose pants, or school uniforms worn without attention to formality. Her androgynous fashion sense and confident posture contribute to her “delinquent” reputation.

Despite her intimidating aura, she carries a subtle grace and presence that hints at deep inner pain and wisdom. She rarely smiles, and when she does, it’s often sardonic or bittersweet.

Nagi is stoic, intelligent, and fiercely independent, guided by a personal code of justice that sets her apart from her peers. She is quick to act, often stepping into danger without hesitation, and views herself as a protector of humanity someone who must act because others cannot or will not. Though she often appears cold or antisocial, Nagi is deeply empathetic and carries the weight of the world’s suffering on her shoulders.

She rejects authority, challenges conformity, and is not afraid to stand alone in the face of threats supernatural or societal. Her approach to life is grounded in rationalism, moral strength, and existential awareness, making her one of the series’ most emotionally and philosophically complex characters.

• The Fire Witch
  Within her school, Nagi is feared and revered as the Fire Witch, a title that mirrors both her temperament and her destiny as the vessel of Walpurgis. While unaware of this identity at first, Nagi instinctively investigates anomalies psychic phenomena, synthetic humans, and other Enemies of the World placing her on a collision course with Boogiepop and the Towa Organization.

• Repent Walpurgis
  In the Repent Walpurgis arc, Nagi takes center stage. It is revealed that she is the host of Walpurgis, a primal and powerful force destined to combat Alcestis, the Witch of Ice. These two forces represent cosmic dualities destruction and stasis, passion and apathy and their struggle echoes through Nagi’s psyche and the world around her. Despite the power within her, Nagi seeks not domination but balance. Her journey is one of self-discovery, restraint, and reclaiming agency in the face of a destiny she never asked for.

• Ally of Boogiepop
  Though their methods differ, Nagi becomes a parallel protector to Boogiepop, sometimes working independently, sometimes unknowingly aiding his missions. Their relationship is one of mutual recognition both are “automatic existences” in a sense, driven to eliminate existential threats to humanity.