Baikoku KikanThe queen of the opera ; Treason Agency ; Treason Agency ~The queen of the opera~ ; 売国機関

In the early 20th century, a small republic found itself stuck between a kingdom and an empire - both of whom wanted to manipulate the republic to suit their own needs.In order to protect itself from both sides of the conflict, the republic created a small group of soldiers whose job it is to suppress revolution and dissent in any way possible. This is the story of the Opera House.