The emperor of Japan is Emperor Akihito, and the prime minister of Japan is Shinzo Abe. Emperor Akihito has a largely ceremonial role, while Prime Minister Abe is the head of government and is effectively the leader of the country.
Japan also has a legislative branch and a judicial branch of government. The legislative branch consists of a parliament called the Diet, which is comprised of the House of Representatives and the House of Councilors. The Prime Minister must be a member of the Diet and is elected by fellow members. The judicial branch of government is made up of a supreme court and a set of inferior courts.