Nazuna is a ten-year-old girl who serves as the shrine maiden of the Shinryu Shira Shrine in Kyoto, a shrine associated with the Heaven Style faction of onmyoudou. She is a Toujinshi, a warrior who contracts with a shikigami, and her partner is Holly, a shinigami that takes the form of a female rabbit. Her duties as a shrine maiden and her role as a Heaven Style user form the core of her background, tying her to the spiritual and martial conflicts of the story.

In terms of personality, Nazuna is a diligent and responsible child, often displaying a maturity that belies her age. She is capable of managing the shrine on her own and takes charge of daily tasks such as cooking for Riku and Souma after she moves into the same apartment building. However, she also possesses a stubborn and somewhat inflexible side. She can be quick to express disapproval and hold firm to her convictions, especially when she perceives a threat or an injustice. Her interactions are marked by a sharp tongue and a tendency to clash with those who challenge her views, though this is often a cover for her underlying care and concern for others.

Her primary motivation is to protect the balance between the Heaven and Earth styles and to fulfill her duties as a Heaven Style user. She is deeply committed to the preservation of her traditions and the safety of her friends, particularly Riku and Souma. Initially, she is suspicious of Souma due to his Earth Style affiliations and strongly opposes Riku's friendship with him, believing it to be dangerous. Over time, she learns to set aside her prejudice and comes to see Souma as an ally and, eventually, someone she cares about deeply, even if she struggles to express those feelings openly.

Nazuna's role in the story is that of a key supporting character and a stabilizing presence within the main group. She is one of the few characters who is immediately suspicious of Masaomi, the older mentor figure, sensing something untrustworthy about his actions long before others do. She also serves as a domestic anchor for Riku and Souma, providing meals and a sense of normalcy amid the chaos of battle. In the latter part of the series, her role becomes more directly active as she uses her knowledge of secret techniques to aid in the resolution of the conflict.

Her relationships are central to her development. With Riku, she is initially distant but grows into a dependable caretaker and ally. With Souma, the dynamic is more complex. They are often at odds, bickering and arguing like typical children, yet there is an underlying mutual awareness and affection that neither is willing to admit. This rivalry and hidden fondness form a notable part of her emotional arc. She also has a confrontational relationship with Momo, who she sees as overly clinging to Riku, and she actively works to keep Momo in check.

Throughout the series, Nazuna undergoes subtle but meaningful development. She moves from a rigid, prejudiced stance against the Earth Style to a more open and cooperative attitude, eventually trusting Souma fully. She also grows more comfortable in her role, no longer just a shrine maiden but a fighter who contributes directly to the group's success. After the war concludes, she returns to the Shinryu Shira Shrine and uses her abilities to send Masaomi and the others back to their original era, demonstrating her mastery and her acceptance of her responsibilities.

Notable abilities include her contract with the shinigami Holly, whom she summons to fight in battle. As a Heaven Style user, she is proficient in the use of onmyoudou seals and techniques. She is also capable of using a secret art known as Koku-watari, a form of time crossing or time travel, which she accesses through a special mirror. Beyond combat, she is highly intelligent for her age, having completed a correspondence course equivalent to a middle school education, and she holds an eighth-degree rank in calligraphy, reflecting a disciplined and scholarly side to her character.