Koike is one of the very few women who hold senior government posts in Japan, where society remains male dominated and many retain the view that a women's place is in the home.
She has introduced a suite of schemes in recent years aimed at empowering other women in the workplace by providing the space to network and develop management know-how that in the past was often only available to men.
"There's no other country in the world where women's power is so underutilised," Koike told Reuters in an interview in conjunction with International Women's Day, celebrated on March 8.
"How to make use of women's untapped energy is important for Japan and for Tokyo."
Over the past decade, under pressure from the Japanese government and Tokyo Stock Exchange, many Japanese companies have succeeded in boosting the number of female executives.
But despite this progress, Japanese women with management responsibilities are severely under-represented at the vast majority of firms, female leaders say.
In a bid to increase the number of women managers, the Tokyo Metropolitan Government has held "career up support" seminars for women since 2018, with the number of participants jumping more than fourfold to nearly 1,400 in the four years to 2022.
"Unfortunately, there are not many role models in Japan for women in management positions or as CEOs making decisions," Koike said.
"As is the case with men, having a good mentor is very effective. And having a network of contacts in different industries is often helpful for all parties," she added.
Koike is not alone. Etsuko Tsugihara, chair of the diversity, equality and inclusion committee at Japan's largest business lobby, Keidanren, is also trying to showcase a different face of corporate Japan, in a bid to provide better role models for women.
Last month, Tsugihara, who is also CEO of public relations firm Sunny Side Up Group 2180.T, led a cohort of female executives of Keidanren companies on a study mission to the United States, meeting with government agencies, U.N. bodies, companies and investors.
Participants included executives from Toyota, Sumitomo Mitsui Banking Corporation, Mitsui & Co. and ANA.
"Keidanren gatherings have really gone from dark suits and grey suits to become colourful," she said, recalling that only a few years ago any business gathering in Japan was almost entirely made up of men in business suits.
As much as she wants her success to encourage other women, Tsugihara said women should not follow her example, and that of many others, and push themselves too hard at work.
Tsugihara recalls working until the day she gave birth, and then having a work meeting at the hospital two days later.
"Far from admiring my efforts, other women told me they didn't want to be like me," she said. "My generation has to be happy, we have to enjoy our work, otherwise other women won't follow."
