Baikoku Kikan is a Manga/Manhwa/Manhua in english language, Seinen series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

n 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.