Tokyo voters cast ballots to decide whether to reelect conservative as city's governor
The vote was also seen as a test for Prime Minister Fumio Kishida's governing party, which supports the incumbent, the first woman to lead the Tokyo city government.
Tokyo, a city of 13.5 million people with outsized political and cultural power and a budget equaling some nations, is one of Japan's most influential political posts.
A record 55 candidates challenged Koike, and one of the top contenders was also a woman — a liberal-leaning former parliament member who uses only her first name, Renho, and was backed by opposition parties.
A win by Koike would be a relief for Kishida's conservative governing party, which she has long been affiliated with. Kishida's Liberal Democratic Party and its junior coalition partner, Komeito, unofficially backed her campaign.
Renho, running as an independent but supported by the main opposition Constitutional Democratic Party of Japan and the Japanese Communist Party, slammed Koike's connection with Kishida's party, which has been hit by a widespread slush fund scandal. A victory for Renho would be a major setback for Kishida's chances in the governing party's leadership vote in September.
While the two high-profile women garnered national attention, Shinji Ishimaru, a former mayor of Akitakata town in Hiroshima, was seen to have gained popularity among young voters.
The main issues in the campaign included measures for the economy, disaster resilience for Tokyo and low birth numbers. When Japan's national fertility rate fell to a record low 1.2 babies per woman last year, Tokyo's 0.99 rate was the lowest for the country.
Koike's policies focused on providing subsidies for married parents expecting babies and those raising children. Renho called for increased support for young people to address their concerns about jobs and financial stability, arguing that would help improve prospects for marrying and having families.
Another focus of attention was a controversial redevelopment of Tokyo's beloved park area, Jingu Gaien, which Koike approved but later faced criticism over its lack of transparency and suspected environmental impact.
Koike, a stylish and media savvy former TV newscaster, was first elected to parliament in 1992 at age 40. She served in a number of key Cabinet posts, including environment and defense ministers, as part of the long-reigning Liberal Democratic Party.
Renho, known for voicing sharp questions in parliament, was born to a Japanese mother and Taiwanese father and doesn't use her family name. A former model and newscaster, she was elected to parliament in 2004 and served as administrative reform minister in the government led by the now-defunct Democratic Party of Japan.