Movie
Description
Izumi Nase served as the previous head of the Nase clan, a family of Spirit World Warriors tasked with managing supernatural phenomena and youmu within their territory. As the eldest sibling in a household without parents, she took on the role of mentor to her younger brother and sister, Hiroomi and Mitsuki Nase, instructing them in the ways of their duty through methods often perceived as harsh.

She carried herself with an elegance befitting her station, paired with a frank demeanor and a characteristically kind expression. Her motherly appearance featured neck-length black hair typically worn down, purple eyes, a small beauty mark below her mouth, and a usual attire of shorts and long-sleeved shirts accessorized with necklaces and a bracelet.

In her capacity as clan head, Izumi represented the family in dealings with the Spirit World Warriors Society, working to maintain her clan's power against the Society's influence. This required political maneuvering, such as permitting Miroku Fujima to observe the Hollow Shadow youmu to stall the Society, though she later actively opposed him when his actions threatened the balance.

Driven by an intense sense of duty, she frequently bore burdens alone, excluding her siblings from her plans and struggles. This isolation led to significant decisions, including a plan to eliminate the powerful youmu known as Beyond the Boundary, which was embedded within the half-youmu Akihito Kanbara. She hired Mirai Kuriyama, the last of a clan with blood-manipulating abilities, to assassinate Akihito. When that failed, she persuaded Mirai to sacrifice herself to extract the youmu, an act which resulted in Mirai absorbing Beyond the Boundary but surviving.

Izumi had initially left the clan for a time but returned to guide her siblings. She had previously tasked Hiroomi with capturing or eliminating Akihito, though she intervened upon learning of Miroku's interest in the half-youmu. After a stalemate fight with Miroku, she later tracked down Mirai upon discovering her blood's potential to suppress Akihito's youmu side.

In a pivotal act to protect her family, Izumi took a youmu into her own body from Miroku Fujima. The youmu eventually overwhelmed her, leading to a loss of control. Her condition was publicly exposed by Miroku in front of Hiroomi, revealing her as a human host. Following this, Izumi vanished into self-imposed exile, leaving clan leadership to Hiroomi.

She later reappeared as a hooded figure in a black bodysuit, wielding her signature double-edged naginata. The youmu inside her had largely taken over, though she experienced moments of clarity. She fought Hiroomi and Akihito while questioning Mirai about her past. With Hiroomi's help, she ultimately overcame the youmu's influence. Her recovery was shown afterward, though her return to leadership remained unclear.

Izumi was an exceptionally skilled Spirit World Warrior, even among her elite clan. She was one of the few capable of using Glaciate Barriers, a technique that could sink a target's consciousness into a dormant state. She also mastered her primary weapon, a double-bladed naginata that could separate into a three-section staff linked by a chain.