Kuro Kagami attends Futatsubashi Elementary School as a short-tempered, diminutive classmate of Rin Kokonoe and Mimi Usa. The trio bonded as "class misfits" during first-grade physical education, remaining close friends since. Initially depicted as a stereotypical spoiled rich child, Kuro displays egotism, a superiority complex, and a tendency to mock others. Her affluent background as an only child with an overworked, frequently absent mother enabled her indulgence in expensive fashion trends, notably Gothic Lolita styles, sometimes accessorized with nekomimi ears and tail. She explicitly selected public school to evade dress code restrictions.

Early on, Kuro treated Rin less as a peer and more as a living doll for dress-up and makeup. This dynamic fractured when Kuro attempted to remove a handmade dress from Rin's mother, triggering Rin's first emotional outburst since her trauma-induced muteness. The incident sparked Rin's recovery and fundamentally altered Kuro's perspective, fostering genuine admiration for Rin's emerging strength. This admiration deepened into an intimate, unrequited romantic attraction, recognized only by Mimi Usa. Kuro's feelings intensified her fierce protectiveness over Rin and anyone she considered a friend.

Kuro retained elements of her volatile nature, including foul-mouthed remarks and physical aggression, particularly directed at teacher Daisuke Aoki. Viewing him as a rival for Rin's affection, she derided him as incompetent, naïve, and a "virgin" lolicon. Her contempt stemmed from perceiving his student concern as insincere—either flattery for authority or hollow obligation—and her general distrust of men, rooted in her father's infidelity and her parents' subsequent divorce. Despite this animosity, Kuro confronted Aoki about his inability to address Rin's emotional needs, declaring he couldn't "banish her friend's demons" without offering romantic love. Though heartbroken by Rin's choice of Aoki, Kuro attempted to temper her hostility for Rin's sake.

Conversely, Kuro idolized the strict teacher Sae Shirai, interpreting Sae's no-nonsense demeanor as authenticity. She cultivated a genuine, albeit occasionally rocky, friendship with Sae, demonstrating her capacity for respect toward figures she deemed sincere.