The Prime Minister of Japan is the head of government of Japan. He is appointed by the Emperor of Japan after being designated by the Diet from among its members, and must enjoy the confidence of the House of Representatives to remain in office. He is the head of the Cabinet and appoints and dismisses the Ministers of State; the literal translation of the Japanese name for the office is Minister for the General Administration of the Cabinet.
The office was created in 1885, four years before the enactment of the Meiji Constitution. It took its current form with the adoption of the current constitution in 1947.
The Prime Minister is designated by both houses of the Diet, before the conduct of any other business. For that purpose, each conducts a ballot under the run-off system. If the two houses choose different individuals, then a joint committee of both houses is appointed to agree on a common candidate. Ultimately, however, if the two houses do not agree within ten days, the decision of the House of Representatives is deemed to be that of the Diet. Therefore, the House of Representatives can theoretically ensure the appointment of any Prime Minister it wishes. The candidate is then formally appointed to office by the Emperor.
The Prime Minister must resign if the House of Representatives adopts a motion of no confidence or defeats a vote of confidence, unless the House of Representatives is dissolved within ten days.