The changes to the Upper House electoral system, enacted this week so they can be in effect for the next election in 2016, are far from a fundamental reform in terms of correcting the sharp disparity in the value of votes between populous and less populous districts. But the protracted discussion over the issue, which split the ruling alliance of the Liberal Democratic Party and Komeito, also suggests that a fundamental solution may have to involve reviewing and possibly redefining the role of the upper chamber under the bicameral system.

Since its inception in 1947, members of the House of Councilors have been elected through a combination of prefecture-based districts and one nationwide constituency — the latter was replaced in the 1980s by today's proportional representation system. Half of the Upper House seats come up for election every three years. This system has created a steep gap in the value of votes between electoral districts, which the Supreme Court ruled were in "a state of unconstitutionality" in the 2010 and 2013 elections.

The revised Public Offices Election Law, jointly endorsed by the LDP, Ishin no To (Japan Innovation Party) and three other parties, for the first time redraws constituencies across prefectural borders. The Tottori and Shimane districts as well as the Tokushima and Kochi constituencies will be combined into two districts — with the total number of seats allocated to them reduced by half. In addition, two seats each will be taken away from Miyagi, Niigata and Nagano prefectures, while two each will be added to Hokkaido, Tokyo, Aichi, Hyogo and Fukuoka.