Set in a fictionalized version of 1923 in the Taishō era, 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 leader of its all-female Flower Division, a group of women with magical abilities that defend Tokyo against demon attacks using steam-powered armor called Koubus. He becomes embroiled in both the group's latest conflict with the Hive of Darkness and the personal lives of its members.