Royal Government

The Ōsei (王政) is the ruling system over the people of Paradis. From the capital of Mitras, the false Fritz monarchy had for the past hundred years acted as the face of the Royal Government while the Reiss family, formerly the true Fritz family, acted as the secret ruling bloodline. After the coup d'état, a majority of the old government was displaced in favor of a military-led system with the Reiss family ruling publicly. Historia Reiss is currently in command as Queen of the Walls.

Structure
Prior to the coup d'état, the Royal Government is outwardly led by a puppet king Fritz, who is unrelated to the Reiss family, the true descendants of Karl Fritz. The officials who make up the rest of Fritz's royal government are different from the majority race that comprises the bulk of the population within the Walls, which makes them immune to the mind-altering abilities of the Founding Titan. They are likely Eldians of minority races who curried favor with Karl Fritz in order to obtain their families' positions.

History
It is said that the Royal Government held significance over humanity even before the Titans first appeared; the royal bloodline having been unbroken for as many as 2,000 years.

During the reign of Uri Reiss, one of the noblemen of the Assembly informed Kenny Ackerman of the Reiss family's true royalty. After Kenny's attempt to assassinate Uri failed, this nobleman was removed from the Assembly and Kenny took his place.

The Uprising arc
After the operation where Eren Yeager was rescued from Reiner Braun and Bertolt Hoover, the Assembly summons Erwin Smith to the chancellery in Mitras. During his meeting with the Assembly, Erwin concludes that the nobility within the Royal Government cares only for their own positions and possessions, giving no regard to humanity as a whole. Conspiring with Dot Pixis, together they plan to overthrow the monarchy and appoint a new leader who will work towards the betterment of humanity and allow the Survey Corps to continue its attempts to reach Shiganshina District.

The opportunity to overthrow the Royal Government comes when Erwin Smith receives the news that the Reiss family is the true royal bloodline. After sending the Survey Corps to search for Rod Reiss, the true king of humanity, Erwin Smith is arrested by the Military Police Brigade, framed for orchestrating the murder of Dimo Reeves. When he is brought before King Fritz, the meeting is interrupted by Anka Rheinberger bringing false news that Wall Rose has fallen and Stohess District was under attack. The Assembly decides to close off the gates of Wall Sheena, refusing to accept any refugees. With this proof of the Royal Government's selfish nature, Commander-in-Chief Darius Zackly arrests the nobility and dethrones the Fritz monarchy.

Control over the nation of the Walls is given over to the military. After the death of Rod Reiss outside of Orvud District, Historia Reiss is publicly crowned as the new monarch of the Walls. Members of the military take over the positions of the former Assembly.