what kind of voting system does japan have?
Parliamentary system Unitary state Constitutional monarchy
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 The Constitution of Japan does not specify the number of members of each house of the Diet , the voting system , or the necessary qualifications of those who may vote or be returned in parliamentary elections , thus allowing all of these things to be determined by law . However it does guarantee universal adult suffrage and a secret ballot . It also insists that the electoral law must not discriminate in terms of " race , creed , sex , social status , family origin , education , property or income " . 

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 Generally , the election of Diet members is controlled by statutes passed by the Diet . This is a source of contention concerning re @-@ apportionment of prefectures ' seats in response to changes of population distribution . For example , the Liberal Democratic Party had controlled Japan for most of its post @-@ war history , and it gained much of its support from rural areas . During the post @-@ war era , large numbers of people were relocating to the urban centers in the seeking of wealth ; though some re @-@ apportionments have been made to the number of each prefecture 's assigned seats in the Diet , rural areas generally have more representation than do urban areas . The Supreme Court of Japan began exercising judicial review of apportionment laws following the Kurokawa decision of 1976 , invalidating an election in which one district in Hyōgo Prefecture received five times the representation of another district in Osaka Prefecture . The Supreme Court has since indicated that the highest electoral imbalance permissible under Japanese law is 3 : 1 , and that any greater imbalance between any two districts is a violation of Article 14 of the Constitution . In recent elections the malapportionment ratio amounted to 4 @.@ 8 in the House of Councillors ( census 2005 : Ōsaka / Tottori ; election 2007 : Kanagawa / Tottori ) and 2 @.@ 3 in the House of Representatives ( election 2009 : Chiba 4 / Kōchi 3 ) . 

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 Following the end of World War II , the Constitution of Japan was adopted as an intention to replace the previous Imperial rule with a form of Western @-@ style liberal democracy . 

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 The houses of the Diet are both elected under parallel voting systems . This means that the seats to be filled in any given election are divided into two groups , each elected by a different method ; the main difference between the houses is in the sizes of the two groups and how they are elected . Voters are also asked to cast two votes : one for an individual candidate in a constituency , and one for a party list . Any national of Japan at least 20 years of age may vote in these elections , which will be changed to 18 in 2016 . Japan 's parallel voting system is not to be confused with the Additional Member System used in many other nations . 

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 The House of Representatives of Japan ( 衆議院 ) is the Lower house , with the members of the house being elected once every four years , or when dissolved , for a four @-@ year term . As of December 24 , 2014 , it has 475 members . Of these , 180 members are elected from 11 multi @-@ member constituencies by a party @-@ list system of proportional representation , and 295 are elected from single @-@ member constituencies . 238 seats are required for majority . The House of Representatives is the more powerful house out of the two , it is able to override vetoes on bills imposed by the House of Councillors with a two @-@ thirds majority . It can , however , be dissolved by the Prime Minister at will . Members of the house must be of Japanese nationality ; those aged 18 years and older may vote , while those aged 25 years and older may run for office in the lower house . 
