I prepared for war against Dorgania but it won't let me start the Kurohime mission so that she becomes a vanguard leader. Also it let me access the scene on the overview map without Kurohime being a vanguard leader.
If you have advanced the events with Grey and Lady Akira, and you told Theremis to prepare a war against Dorgania, a spy mission should be available at Lualombo with Kurohime, which'll unlock her as a recruitable squad leader.
I'm aware of a bug with her scene and events, and will fix those problems.