(CNN)One of the world's most unequal parliaments could be about to get a lot more female, or ... maybe not.
Voting is underway in Japan's general election, where a record number of women are running for office to fill 124 of the 245 seats in the upper House of Councilors.
Half of the upper chamber of the National Diet is elected every three years and this election includes three new seats.
Of the 370 candidates running this year, 104 -- or almost 30% -- are women, according to public broadcaster NHK.
The increase seems promising for advocates of gender equity. However, if the ruling Japanese Prime Minister Shinzo Abe's ruling Liberal Democratic Party (LDP) retains it dominance, the election could result in a barely perceptible shift.
That's because many of the female candidates are members of smaller, left-wing parties, the Constitutional Democratic Party (CDP) and the Japanese Communist Party (JCP).
The ruling LDP is fielding as many candidates as the CDP and JCP combined, but only 14.6% of their candidates are women.
That means, if the House of Councilors retains its current party makeup, women will hold around 21% of the seats, compared to 20% currently.
That's a lot better than the 10% of women members in the lower house, which does not go to the polls until 2021.
Under the LDP and Abe, Japan has slipped to being the least representative G20 nation for women and among the worst in the world as measured by proportion of female lawmakers.
After winning re-election in 2017, Abe appointed just one woman to his cabinet, despite a promise to focus on improving the country's gender gap through "womenomics."
Last year, a law was passed encouraging political parties to set targets for gender parity. However, there are no incentives or penalties for parties which fail to do so.
At local level, women comprised 17.2% of large municipal assemblies and 14.9% of smaller city assemblies in December 2017. But they only made up 10.1% of prefectural assemblies and 9.9% of town and village assemblies, according to data from the Gender Equality Bureau Cabinet Office.
"Female politicians in Japan must battle against the commonplace view that politics belongs to men," Fujie Masahiro, a section leader at the Gender Equality Bureau Cabinet Office, told CNN in March. "They also face barriers when it comes to juggling family and political life."