Mifuyu Kisaragi hails from the influential Kisaragi family, whose significant standing in finance grants her wealth and political connections. She attends Flawless Academy, the elite all-girls department of Sosei Academy, where she holds a leadership position akin to a prefect or "Milady." In this role, she acts as an elder sister figure, demonstrating genuine care for fellow students like actively befriending the shy Yumina Takanashi. Physically, she stands 169 cm tall with a slim build, pale skin, blonde hair often featuring distinctive spiky bangs or side tails, and violet tsurime-shaped eyes. Her elegant attire consistently mirrors her refined status, incorporating elements such as skirt suits, pantyhose, high-heeled shoes, hairpins, bracelets, and ribbons.

Her personality blends intelligence and calmness with a proactive, serious demeanor. This combination sometimes leads to misunderstandings despite her fundamentally kind nature and consistent efforts to find optimal solutions for others. Initially, she displays deep skepticism or hostility towards Yuuri Mito and the existence of Tayutai, demanding irrefutable proof of Mashiro's supernatural nature and even attributing Mashiro's claims to delusions. However, witnessing undeniable evidence of Tayutai firsthand sparks significant development. She apologizes to Yuuri, acknowledges the reality of human-Tayutai coexistence, and becomes a committed political representative and advocate for Mashiro Mito's vision of harmony.

Mifuyu possesses formidable combat prowess, highly skilled in various martial arts with particular expertise in kenjutsu (Japanese swordsmanship). This makes her physically powerful enough to directly confront and battle Tayutai. A key aspect is her relationship with the Tayutai Nue. After initially confronting and helping defeat Nue alongside Mashiro, she forms a strong bond with her. They are often seen together in a dynamic resembling a mother-daughter relationship, with Mifuyu assuming a caring, guardian-like role for Nue. She maintains connections with the Mito family, having known both Yuuri Mito and Mashiro Mito since her student days, and stands among the earliest humans to establish communication with Tayutai.