Kanzaki was born with the abilities of a Saint, making her one of the most powerful magicians in existence. As a member of the Amakusa-Style Remix of Church, she was raised within their unique magical traditions, which blended Christian, Shinto, and Buddhist influences. However, due to her overwhelming strength, she felt out of place among them, believing that her presence endangered her comrades. This led her to leave the Amakusa Church and join Necessarius, where she was assigned to protect Index alongside Stiyl Magnus.

Her beliefs were shaken when she learned that Index’s annual memory erasure was unnecessary, making her complicit in the Church’s deception. This realization left her with deep guilt, forcing her to reconsider her faith and her duty. Although she remained with Necessarius, she never completely severed ties with the Amakusas, and eventually, when they were integrated into Necessarius, she returned to them as their leader, embracing her responsibility to protect them.

Kanzaki Kaori is a tall, striking woman with long, dark blue hair, which she ties into a low ponytail with a red ribbon. She has sharp violet eyes and a well-toned physique, reflecting her combat training and physical prowess.

She typically wears a simple white blouse and blue jeans, an outfit that contrasts with the robes and ceremonial attire worn by most magicians. Her choice of clothing reflects her practical nature, prioritizing mobility over formality. Additionally, she carries her signature weapon, the Seven Heavens Seven Swords (Nanatsu no Yoru no Ken), though she rarely unsheathes it, as her raw physical strength is usually more than enough to overpower opponents.

Kanzaki Kaori is calm, disciplined, and highly self-aware, carrying herself with grace and maturity even in tense situations. She is deeply loyal to those she cares about but often struggles with guilt and self-doubt, particularly when her duty conflicts with her personal emotions. Unlike many magicians who act on ideology or self-interest, Kanzaki is practical and level-headed, preferring to find peaceful solutions before resorting to violence.

Despite her incredible power, she is humble and reluctant to use excessive force, fearing that her abilities might unintentionally harm others. This restraint is best seen in her hesitation to wield her sword, as she believes drawing it should only be a last resort. However, when threats arise, she is ruthless and efficient in battle, demonstrating why she is considered one of the most dangerous Saints in existence.

Although she appears composed, Kanzaki has moments of vulnerability, especially when interacting with Index or the Amakusas. She longs for a sense of belonging, which is why her eventual return to the Amakusa Church is so meaningful. Her stoic and caring nature, combined with her unparalleled strength, makes her one of the most respected figures on the Magic Side.

• Guardian of Index and First Encounter with Touma
  Kanzaki is introduced as one of Index’s original guardians, assigned by Necessarius to ensure her safety alongside Stiyl Magnus. Initially, she follows orders without question, believing that Index’s memory must be erased annually to prevent magical corruption. However, after Kamijou Touma discovers the truth, she realizes that the Church had deceived her, leaving her guilt-ridden and questioning her allegiance. During her first encounter with Touma, she fights him in an attempt to retrieve Index, showcasing her overwhelming power as a Saint. However, Touma manages to hold his own, proving that strength alone does not determine victory. Though she initially views him as reckless, she comes to respect his determination and later supports him in battles against powerful magical threats.

• Return to the Amakusa Church
  Although she had separated from the Amakusa Church, Kanzaki continues to care for them from afar. When the Amakusas later join Necessarius, she finally reunites with them, taking on the role of leader once again. This decision marks a turning point in her character arc, as she learns to embrace her identity rather than run from it. As a leader, warrior, and protector, Kanzaki serves as a key player in magical conflicts, battling high-level magicians, Saints, and supernatural threats while ensuring the safety of both Index and the Amakusas.