The Public Offices Election Law actualizes the principles contained in the Constitution, in stipulating the fundamental points relating to the elections of national and local public offices. Previously, there was no unified legislation on elections; each election, national or local, was held under the rules of individual acts (the Lower House Election Law, the Upper House Election Law and the provisions concerning the election of local authorities in the Local Autonomy Law). In 1950, all these acts were consolidated into the Public Offices Election Law.
On 4 and 17 June 2015 respectively, the House of Representatives and the House of Councilors adopted a bill to amend the Public Offices Election Act, which includes a provision to lower the voting age from 20 to 18 years old. The Act was promulgated by the Cabinet on 19 June 2015 and will be applied to national elections the start of whose campaign period is announced one year after that date (i.e., any election with a campaign period announced after 20 June 2016 and whose polling day falls after 7 July 2016).
The legislative framework governing democratic representation is as follows:
-Constitution of Japan
-The Public Offices Election Law (1950)
-The Local Autonomy Law
Japan has signed and ratified key international instruments relating to the conduct of elections, including UN Declaration of Human Rights, International Covenant on Civil and Political Rights, Convention on the Elimination of All Forms of Discrimination against Women, International Convention on the Protection and Promotion of the Rights and Dignity of Persons with Disabilities, and Convention on the Rights of Persons with Disabilities.
Reference:
Election System in Japan, Local Governance (Policy Making and Civil Society F.Y. 2007)
Inter-Parliament Union, Japan, http://www.ipu.org/parline/reports/2161_B.htm.
University of Minnesota, Ratification of International Human Rights Treaties, Indonesia, https://www1.umn.edu/humanrts/research/ratification-indonesia.html.
Resources :
Constitution
PDF : Constitution of Japan (Web Japan: Fact sheet)
Electoral law
PDF : New Disability-Related Law of Japan: Amendment to the Public Offices Election Law
Analysis on legal framework