The Black Bunker (黒要塞, Kuro Yousai) is the Kurokami Group's South Pole base, and serves as the second stage of the second Jet Black Wedding Feast. Medaka Kurokami was confined there for a short time by Bukiko Udou, but the base was abandoned to keep Medaka separated from Zenkichi Hitoyoshi.
The interior is standard for a polar base. It has undecorated walls with the pipes still bare. It has a storage room that holds cardboard boxes and books, suggesting that the base is somewhat old. There is at least one cell with chains for restraining a prisoner.