Japan has a parliamentary government headed by a prime minister and a constitutional monarchy headed by the emperor. Like the United States government, the government of Japan has three branches: executive, judicial and legislative.
While nominally shared between the emperor and the prime minister, in practice, the executive branch of government is largely the domain of the prime minister, who is responsible for a range of constitutional duties, such as signing laws and proposing bills. The emperor serves in more of a symbolic capacity, similar to the Queen of England. The role of prime minister is subject to public election every 4 years, whereas the role of the emperor is inherited.
The judicial branch is headed by the Saiko Saibansho, Japan's equivalent of the Supreme Court. The supreme court chief justice, whose election cycle lasts 10 years, is responsible for upholding the constitution.
The legislative branch is represented by the National Diet, which is responsible for approving budgets, making laws and drafting constitutional amendments. The branch is split into the lower 480-seat House of Representatives and the higher 282-seat House of Councillors, which has greater powers and can delay the lower houses' budget or treaty decisions. The minimum age for voting in Japan is 20.