• Annual reports - Government of Japan
• Budgets and settlement of accounts
• Cabinet Decisions
• Decorations and medals
• Election results
• Fundamental statistics
• Index of Japanese Government Ministries and Agencies
• Information of Diet members
• Information on meetings of the Diet
• Japanese Instructions, Communications, and Notices
• Japanese laws and regulations
• Japanese parliamentary documents
• Judicial precedents
• Legislative bills
• List of websites of Japanese local governments
• Materials of local assemblies
• Official Gazettes
• Official statistics
• Prefectural Statistics
• Statutory documents of local governments in Japan
• Treaties, Resolutions, Petitions, and Statements of Questions / Written Answers
• White Papers

More research guides and sub categories are provided in Japanese page of "Materials of Parliament, Law, Precedent, Public Administration" etc.