Shimane 1st district is a constituency of the House of Representatives in the Diet of Japan.

Due to this, Hosoda himself rarely returned to campaign in the district, but usually won by hefty margins, with no other candidates even winning a spot in the overall Chūgoku proportional representation block (outside of the 2009 Japanese general election, where Toshiaki Komuro managed to win a spot.

In the 2017 Japanese general election, this was cut down to twenty, and Akiko Kamei became the first opposition politician since 2009 to return on a proportional block.

Despite her losing the proportional seat in the 2021 Japanese general election, Hosoda's margin of victory had been cut down to a further fifteen points.

With Hosoda's death and extreme unpopularity relating to his sexual harassment scandals and ties to the Unification Church, the by-election due to occur in April 2024, were projected to be unusually close.