Political parties in favor of revising the Constitution have secured a two-thirds majority in the House of Councillors -- enough to initiate constitutional amendment -- following the July 10 election.
The ruling Liberal Democratic Party (LDP), its junior coalition partner Komeito and Initiatives from Osaka, which favor constitutional revision, won at least 74 seats in the election.
These parties, the Party for Japanese Kokoro and independents backing constitutional revisions hold 88 seats in the chamber that were not contested in the July 10 election. Pro-constitutional revision forces needed to win 74 seats to secure a two-thirds majority in the chamber.
The LDP-Komeito coalition already has more than two-thirds of the seats in the House of Representatives. Under Article 96 of the Constitution, constitutional amendment can initiated by the Diet through a concurring vote of at least two-thirds of all members of each chamber, after which a referendum is held.
Prime Minister Shinzo Abe told a TBS program on the night of July 10, "I'm relieved as the ruling coalition secured a majority of contested seats."
Abe made little mention of constitutional revisions during the election campaign. In the TBS program, Abe only said constitutional amendment is something that should be determined through a referendum.
During the campaign for the election, the LDP emphasized the achievements of the Abenomics economic policy mix promoted by the Abe government, and cited Abenomics as the key point of contention.
The LDP won more than the 50 contested LDP seats in the election, while all seven Komeito candidates who ran in constituencies secured seats. Together, the ruling coalition is certain to win more than 61 seats -- a majority of the 121 contested seats. Prime Minister Abe had set this as the party's minimum goal.
The LDP won in 21 out of 32 constituencies in which only one seat was contested -- a key to its victory. The party won two seats each in the Tokyo and Chiba electoral districts where multiple seats were up for grabs. The LDP, which won 18 seats in the proportional representation bloc in 2013, is expected to win around the same number of seats.
Komeito fielded a record seven candidates in constituencies in which multiple seats were contested and had all candidates in those electoral districts secure seats, although those running for the party faced close contests in constituencies in Saitama and Hyogo. In the proportional representation bloc, Komeito appears likely to win around seven seats, the number of seats the party won in the 2013 race.
The Democratic Party (DP) lost many of its 46 contested seats, but had candidates it supported jointly with three other opposition parties, including the Japanese Communist Party (JCP), win in 11 of 32 constituencies in which only one seat was up for grabs.
Overall, the DP won at least 31 seats -- far more than the 17 it won in the previous upper house election in 2013.
During campaigning, the four opposition parties that combined forces underscored the need to scrap Japan's new security legislation. They also called to block pro-constitutional amendment forces from securing two-thirds of the seats in the chamber.
Opposition candidates defeated two incumbent candidates: Aiko Shimajiri, state minister for Okinawa and Northern Territories affairs, was defeated by Yoichi Iha, who was backed by opposition parties including the JCP and the Social Democratic Party (SDP). In the Fukushima prefectural constituency, Justice Minister Mitsuhide Iwaki lost to DP incumbent Teruhiko Mashiko.
This is the first time since the second Abe Cabinet was launched in December 2012 that incumbent Cabinet ministers have lost their seats in the Diet.
A DP candidate barely won in Mie Prefecture, where its leader Katsuya Okada's home constituency is situated. Okada had hinted at the possibility that he would step down as party leader if the candidate was defeated.
The JCP secured more than the three of its seats up for grabs this time. A JCP candidate won a seat in the Tokyo constituency as it did in the 2013 poll, while the others won their seats through the proportional representation system.
The Initiatives from Osaka party won three seats -- two seats in Osaka and one seat in the Hyogo prefectural constituency, and four in the proportional representation bloc, far more than its two contested seats.
The SDP won just one seat through the proportional representation bloc, while the Party for Japanese Kokoro and the New Renaissance Party are unlikely to win a seat.
It was the first Diet election in which 18- and 19-year-olds cast their ballots.