what is it's popular supreme power or authority?
The Emperor of Japan.
Government of Japan
The Government of Japan is the central government of Japan. The Government of Japan consists of legislature, executive and judiciary branches and is accountable to the Emperor of Japan. 
who does the leader of an absolute government depend on and why UNANSWERABLE mention any historical importance of this place? Prior to the Meiji Restoration, Japan was ruled by the government of a successive military "shōguns". who was the first emperor? UNANSWERABLE who are the members of the cabinet? It consists of the Ministers of State and the Prime Minister. what houses are mentioned here in the government? The House of Representatives and the House of Councillors. how is the former above house different from the latter? The legislative powers of the House of Representatives is considered to be more powerful than that of the House of Councillors. what legislation do they follow? Empowered by the Constitution to be "the highest organ of State power" and the only "sole law-making organ of the State", the Legislative branch organ of Japan houses are both directly elected under a parallel voting system and is ensured by the Constitution to have no discrimination on the qualifications of each members.
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Government of Japan [SEP] Introduction
The Government of Japan is the central government of Japan. The Government of Japan consists of legislature, executive and judiciary branches and is accountable to the Emperor of Japan. The Prime Minister of Japan is the chief executive of the government and is responsible for selecting ministers to serve in the Cabinet of Japan, the executive branch of the state government. 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.