TV-Series
Description
Mitsuki Nase, the youngest sibling in the prestigious Nase clan of Spirit World Warriors, possesses long straight black hair, dark ruby eyes, fair skin, and a slim yet curvy figure, standing 165 cm tall. She typically wears a sailor-style school uniform featuring a yale-blue top, light blue pleated skirt, black calf-length socks, and black-and-white shoes, often seen snacking on sweets like lollipops or popsicles.

She presents a detached, near-sadistic demeanor, speaking frankly and frequently teasing others, especially Akihito Kanbara. This behavior stems from childhood lessons by her older sister Izumi, who taught that Spirit Warriors must prioritize duties over personal connections, leading to Mitsuki's isolated upbringing. Despite this exterior, she experiences deeper emotions like anger, sadness, and happiness. She uniquely believes some Youmu can coexist peacefully with humans, a view differing from traditional clan doctrines. Her fondness for sweets and reliance on her pet Youmu, Yakiimo, for combat further define her.

As a second-year high school student and president of the Literary Club, Mitsuki and her brother Hiroomi were tasked by their clan to monitor the Half-Youmu Akihito Kanbara, forming the club for oversight. After encountering Spirit Warrior Mirai Kuriyama targeting Akihito, Mitsuki initially warns him against interacting with her but gradually accepts Mirai. She assists Mirai in joining the Literary Club and secures her part-time employment after Mirai loses her Spirit Warrior license. Mitsuki's bond with Mirai deepens, including shared experiences like attending a lantern festival.

During the "Calm" arc, Mitsuki detects disturbances affecting Youmu, including Akihito. She investigates the phenomenon linked to the Youmu "Beyond the Boundary" and opposes Izumi's proposal to kill Akihito during his rampage. Later, when Beyond the Boundary resurfaces, Mitsuki fights alongside her siblings and allies to subdue it. The conflict reveals Izumi's secret fusion with a Youmu, leading to her departure and the transfer of clan leadership to Hiroomi and Mitsuki. After Beyond the Boundary's defeat, Mitsuki resumes daily life and reunites with Mirai upon her return.

Mitsuki wields "Glaciate Barriers" for defense and offense against Youmu, but prefers deploying Yakiimo in combat and relies on her siblings' support due to being less proficient than them. Her relationships include a protective yet bickering dynamic with Hiroomi, a friendship with Akihito marked by mutual teasing and genuine concern, and a sisterly affection for Mirai, highlighted by an emotional embrace upon Mirai's return.

Her background reveals a childhood confined to the Nase residence, limiting social interactions. This isolation fostered her initial emotional reserve, which gradually softens through her Literary Club associations. Her development shows increased loyalty to friends and willingness to defy clan expectations, particularly in protecting Akihito and supporting Mirai.