Earth Federation
In this era, most people live on space colonies. In order to protect the environment and prevent pollution, the Earth is, in principle, completely uninhabitable, and the only people who are allowed to live on the planet are federal government employees who monitor the environment. In reality, however, a few privileged people and a large number of illegal residents remain on the planet. In addition, although officially denied, there are industrial production bases scattered throughout the world. In response to this, the MHA (Man Hunting Agency), a secret police, was established within the Earth Federation as a "manhunting unit" to detect illegal residents on Earth. However, the MHA, which was only an internal bureau of the Earth Federation, emerged as a private army based on a kind of elitism, and began to suppress people with anti-Earth Federation ideas.