The Government of Japan consists of legislative, executive and judiciary branches and is based on popular sovereignty. The Government runs under the framework established by the Constitution of Japan, adopted in 1947. It is a unitary state, containing forty-seven administrative divisions, with the Emperor as its Head of State. His role is ceremonial and he has no powers related to Government. Instead, it is the Cabinet, comprising the Ministers of State and the Prime Minister, that directs and controls the Government and the civil service. The Cabinet has the executive power and is formed by the Prime Minister, who is the Head of Government. The Prime Minister is nominated by the National Diet and appointed to office by the Emperor.
The National Diet is the legislature, the organ of the Legislative branch. It is bicameral, consisting of two houses with the House of Councilors being the upper house, and the House of Representatives being the lower house. Its members are directly elected by the people, who are the source of sovereignty. It is defined as the supreme organ of sovereignty in the Constitution. The Supreme Court and other inferior courts make up the Judicial branch and have all the judicial powers in the state. It has ultimate judicial authority to interpret the Japanese constitution and the power of judicial review. They are independent from the executive and the legislative branches. Judges are nominated or appointed by the Cabinet and never removed by the executive or the legislature except during impeachment.
Prior to the Meiji Restoration, Japan was ruled by the government of a successive military shōgun. During this period, effective power of the government resided in the Shōgun, who officially ruled the country in the name of the Emperor. The Shōgun were the hereditary military governors, with their modern rank equivalent to a generalissimo. Although the Emperor was the sovereign who appointed the Shōgun, his roles were ceremonial and he took no part in governing the country.