Diet
The national legislature of Japan.
House of Representatives
the Shuugin (衆議院, House of Representatives) is the lower legislative house.
The lower house can override a vote of the upper house with a two-thirds majority.
House of Councillors
The Sangiin (参議院, House of Councillors) is the upper legislative house.
At formation the house had 250 seats in staggered 6-year terms; half are allocated for election every 3 years. In 1970, two seats were added for Okinawa. Malapportionment reforms passed in 2000 saw 10 seats stripped from the house in phases by 2005. Further reforms passed in 2018 will see 6 seats added in phases by 2022. The new size of the house will be 248 seats.
150 seats are elected from 47 districts which have unequal representation. In any districts with just one contested seat, this system is equivalent to first-past-the-post. 6 seats were stripped from this amount in 2000, while 2 were added in 2018.
100 seats were elected from a national block (全国区), in staggered amounts of 50 per election. In 1983 this was replaced with a 100-seat proportional district (比例区) based on party lists. The aforementioned malapportionment reforms saw two seats were stripped away in the 2001 and 2004 elections each. Two seats were added back in the 2019 election, with another two to be added back in the 2022 election.
In 2005, Prime Minister Koizumi established a precedent for dissolving the House of Representatives after a vote of no confidence in the House of Councilors.