Yasuna Kamiizumi emerged from a wealthy family where her parents initially supported her but grew distant due to business demands. From early childhood, a physiological affliction prevented her from seeing male faces clearly; they appeared only as indistinct, hazy blurs. This condition affected male teachers and classmates, leading to social isolation as she struggled to connect. Her inability to see her own father strained their relationship, deepening her solitude. She resigned herself to a solitary existence, believing she required no friendships.

Her appearance embodies a delicate, fairy-like aesthetic. Teal eyes shift to deep green during emotional moments, complementing long black hair featuring gray and lavender highlights, often styled with a Lolita hairband. She carries herself with regal refinement and favors ultra-feminine clothing, typically Lolita-inspired dresses or her school uniform: a blouse with a bow tie, jumper dress, and knee-high socks. This presentation underscores her focus on femininity, conveying sophistication without overt opulence.

Personality-wise, Yasuna embodies refined appreciation for classical music, fine arts, and nature, alongside a spiritually minded disposition emphasizing kindness and Agape love. Yet her affliction fostered profound loneliness, low self-worth, and social awkwardness, hindering lasting connections. She exclusively engaged with females, ignoring masculine elements. Her life shifted upon encountering Hazumu Osaragi, initially perceived as male but whose face she could partially discern—a first. This anomaly hinted at Hazumu's underlying female gender identity. Though developing feelings, Yasuna rejected his pre-transformation confession, fearing eventual loss of vision and emotional devastation.

Following Hazumu's accidental gender transition via alien intervention, Yasuna immediately confessed her love, seeking to rectify her prior rejection. Her devotion intensified, leading her to join Kashima High's music ensemble as an accomplished flutist; peers noted her increased approachability. She openly expressed desires for exclusivity with Hazumu, culminating in initiating their first kiss. Across media, her romantic pursuit varied: the manga depicted her actively vying for Hazumu against rival Tomari Kurusu, while the anime initially portrayed her avoiding Hazumu post-transition before reconciling.

Her character arc diverged significantly by medium. The manga featured Yasuna in a love triangle resolved when Hazumu chose Tomari after a life-grain donation saved her life. The anime diverged by having Hazumu choose Yasuna to alleviate her deteriorating vision, which had begun affecting her sight of females. Yasuna's sight fully recovered through this relationship, enabling her to perceive all genders. However, the OVA sequel depicted her ending the romance, asserting newfound independence while maintaining a close friendship with Hazumu. Post-breakup, Hazumu and Tomari married.

Differences in her affliction’s portrayal also emerged. The manga established her lifelong inability to see males clearly, with Hazumu as the sole exception. The anime retconned this, depicting her vision loss beginning after her father’s anger during childhood, later spreading to all males and temporarily worsening to include females. It also emphasized fear-based avoidance of males, contrasting with the manga’s passive indifference.

In the PlayStation 2 visual novel spin-off, Yasuna appeared as a romance option during a summer trip narrative, though her role lacked unique development beyond source material traits.