Kuroki, Misa

黒木美紗

Koizumi's lesbian friend who acts as though they were former lovers. She belongs to a small circle of friends who sell themselves to men, typically with perverse intentions; Koizumi joined the group temporarily while seeking acceptance. Misa does not actually have sex with her "clients"; instead, she teases them and employs her own method to ensure the men never get too far with her.
In the manga, Koizumi makes it quite clear that they were never lovers, with the attraction being fanatically one-sided. Still, Koizumi values Misa's friendship and the protection the girl provided her when she was part of that lifestyle.