The 25th regular election of members of the House of Councillors will be held on July 2019 to elect 121 of the 242 members of the House of Councillors, the upper house of the 717-member bicameral National Diet of Japan, for a term of six years.
76 members will be elected by single non-transferable vote (SNTV)/First-past-the-post (FPTP) voting in 45 multi- and single-member prefectural electoral districts. The nationwide district will elect 48 members by D’Hondt proportional representation with most open lists.
Background
The term of members elected in the 2013 regular election (including those elected in subsequent by-elections or as runners-up) ends on July 28, 2019. Under the “Public Offices Election Act” (kōshoku-senkyo-hō), the regular election must be held within 30 days before that date, or under certain conditions if the Diet is in session or scheduled to open at that time, between 24 and 30 days after the closure of the session and thus potentially somewhat after the actual end of term.
Going into the election, the Liberal Democratic Party and its coalition partner Komeito controls a two-thirds super-majority of seats in the House of Representatives but did not control a similar super-majority of seats in the House of Councillors, necessary to initiate amendments of the Constitution of Japan.
Sources and further reading:
Cloudy Skies Ahead for Abe Shinzō
https://www.nippon.com/en/currents/d00442/
Prospects for PM Abe achieving cherished goal of amending Constitution uncertain
https://mainichi.jp/english/articles/20181025/p2a/00m/0na/017000c