Lawmakers in the Upper House are elected every three years, with half the 242 seats up for grabs each time. Those elected serve a six-year term.
Unlike the Lower House, which is more powerful, the Upper House is never dissolved for an election and its members serve out their terms.
Under the Constitution, the Lower House is granted more power and its decision takes precedence over that made by the Upper House, as it reflects the will of the people more directly with its members serving for a shorter period than Upper House members.
Lower House members often do not serve out their four-year term due to dissolution of the chamber.
Of the 121 seats to be contested in the upcoming election, 73 will be filled by the winners from 47 prefectural electoral districts and the remaining 48 by those chosen under the nationwide party-list proportional representation system, with voters casting two ballots on election day.
Of the 47 electoral districts, 31 are assigned one seat each to be up for grabs, two seats are allocated to 10 prefectures, three seats to Saitama, Chiba and Aichi prefectures, four seats to Kanagawa and Osaka prefectures and the largest number — five seats — to Tokyo.
The number of seats for electoral districts has been adjusted to narrow the disparity in the weight of votes among constituencies.
Under the proportional representation system, voters can either vote for a party or a candidate of their choice from contenders registered by parties under an open-list system.
Seats will be allocated to the parties in line with the total ballots they win in terms of their names or the candidates on their lists.
Candidates will then be ranked within each party according to the number of ballots received under their names. The one with the largest number of votes will be given priority in the allocation of seats for the party.
Under such a system, parties often field candidates known to the public, such as celebrities, scholars or athletes, to draw a large number of votes.
Candidates cannot run in both the electoral district and under the proportional representation system at the same time, unlike in Lower House elections.
Key events during Abe’s watch
Dec. 26, 2012 — Abe takes office as prime minister, launching his second administration after stepping down in 2007.
Jan. 11, 2013 — The government unveils a ¥20 trillion economic stimulus package.
January — A hostage crisis in Algeria ends with the deaths of 10 Japanese citizens among other victims.
Feb. 12 — North Korea conducts its third nuclear test, drawing international condemnation.
Feb. 22 — Abe meets with U.S. President Barack Obama in Washington, taking a step closer to Japan’s participation in the Trans-Pacific Partnership free-trade talks.
Feb. 26 — The Diet enacts a ¥13 trillion extra budget for fiscal 2012 to finance measures to boost the economy.
March 15 — Abe announces Japan will join the TPP talks.
March 25 — Japan and the European Union agree to launch talks for a free-trade agreement.
April 4 — The Bank of Japan decides on bolder monetary easing and introduces a 2 percent inflation goal under new Gov. Haruhiko Kuroda, in line with Abe’s economic policy.
April 29 — Abe meets with Russian President Vladimir Putin in Moscow and the two agree to revive stalled territorial talks.
May 15 — The Diet enacts a ¥92 trillion state budget for fiscal 2013 with focus on Abe’s reform initiatives.
May 26 — Abe pledges ¥91 billion in new development aid for Myanmar during the first visit to the country by a Japanese prime minister in nearly 40 years.
June 3 — Abe pledges to encourage Japanese firms to invest more in Africa at a Japan-hosted conference.
June 14 — The government unveils its latest growth strategy, focusing on lifting the economy out of deflation with more private-sector investment.
June 17-18 — Abe attends the Group of Eight summit in Northern Ireland, where he explains Japan’s efforts to revive the economy and maintain fiscal discipline.
June 23 — Abe’s Liberal Democratic Party sweeps Tokyo assembly election.
June 26 — The Diet closes its 150-day ordinary session.