Fumi Yokomizo works as the school librarian at her former educational institution. She stands 172cm tall with a slim build, pale skin, blonde hair often styled long in buns, ponytails, or curtained looks, and blue, tareme-shaped eyes. Her body measurements are 90-58-87 cm.

Her clothing includes dresses, miniskirts, shirts, jackets, yukata, gym shorts, and swimwear, frequently depicted with a bra. She accessorizes with belts, necklaces, hair ties, and glasses. Personality-wise, she uses masculine speech patterns, engages in adult behaviors like drinking and smoking, and possesses sexual experience.

Within the narrative, she serves as a romance option for the protagonist, characterized by intelligence and maturity relative to others. Approaching her romantically takes persistence due to her initial reserve. Her background centers on transitioning from student to staff at the same school. She has an unspecified connection to Hiroko Hirasawa.