2025 House of Representatives Election Invalidation Case

In October 2025, Japan held a general election for the House of Representatives. Voters from densely populated Tokyo and Osaka districts filed suit at the Tokyo High Court, arguing the election was unconstitutional because the maximum disparity in vote weight between the least and most populous constituencies reached 2.05-fold. The plaintiffs, represented by attorney Hidetoshi Masunaga, sought to invalidate the entire election. After the high court rejected the claim, the case was appealed directly to the Supreme Court of Japan and docketed as Reiwa 7 (2025) Case No. 1 for election invalidation. The Supreme Court Grand Bench, presided over by Chief Justice Yukihiko Imasaki, consolidated the challenge with parallel suits and heard arguments on whether the disparity violated the constitutional principle of equality.

The Supreme Court ruled that the disparity was in an unconstitutional state but declined to invalidate the election, allowing the results to stand while urging the Diet to rapidly address malapportionment.

Whether the 2.05-fold maximum vote-value disparity in the 2025 general election violated the equality requirement under the Japanese Constitution, and whether the court should order a complete invalidation of the election results.

The ruling reignited intense public and political debate over electoral reform and the necessity of mandatory redistricting, reinforcing judicial reluctance to void a concluded national election while placing further pressure on lawmakers to correct vote-weight inequality.