Set in a fictionalized version of the Taishō period, the game follows the exploits of the Imperial Combat Revue, a military unit dedicated to fighting supernatural threats against Tokyo while maintaining their cover as a theater troupe. Imperial Japanese Navy Ensign Ichiro Ogami is assigned as leader of its all-female Flower Division, a group of women with magical abilities which defends Tokyo against demon attacks using steam-powered armor called Koubu. He becomes embroiled in both the group's latest conflict with the Hive of Darkness and the personal lives of its members.