Kaori Izumi, a fourteen-year-old student at Miyagami Private Academy, serves in the Assault Squad of the Best Student Council. With distinctive purple hair and matching eyes, she specializes in bare-handed combat. Secretly harboring romantic feelings for student council president Kanade Jinguuji, Kaori often daydreams about moments with her, fueling intense loyalty. This devotion initially sparks jealousy toward Rino Rando due to Rino's closeness to Kanade, though that jealousy gradually fades as Kaori builds a friendship with Rino upon recognizing their shared traits.

Her character is deeply shaped by family circumstances: orphaned, she shoulders responsibility for her younger siblings, commuting daily instead of residing in council dormitories. Balancing family support, council duties, and academics consumes her time, reinforcing her individualistic tendency to undertake missions alone. When the council discovers her childcare burden, members organize a babysitting schedule during her duties—a gesture that profoundly moves her.

Strong-willed and determined, particularly in impressing Kanade, Kaori maintains good academic standing. Her fierce protectiveness extends beyond the president to council friendships, demonstrating loyalty to peers despite initial reservations about Rino. Through reconciling personal feelings, responsibilities, and relationships, she evolves, overcoming early hostility through understanding.