An influential businesswoman on Monday shocked many working women in Japan by disclosing she is in same-sex relationship, possibly a game-changing event in the nation's slowly growing acceptance of sexual minorities.

Kazuyo Katsuma, a 49-year-old mother of three, was on the Wall Street Journal's list of "The 50 Women to Watch" in 2005 for gaining "legions of fans among Japanese working mothers" through the management of an online forum for working mothers.

(Katsuma (R) and Masuhara [Photo: Twitter]

Her fans are known as "Katsumer," which was nominated as the 2009 buzzword of the year.

Katsuma had previously been married twice.

In an interview with the website BuzzFeed Japan, Katsuma said she has been living with Hiroko Masuhara, a 40-year-old activist for the rights of lesbians, gays, bisexual and transgender people.

"I had kept the lid on my feelings of attraction to members of the same sex," said Katsuma, who has authored a number of best-selling books. According to her website, more than five million copies of her books on work-life balance, self-management and other topics have been published.

"After I met Hiroko, the ice in my heart has melted, although it took a few years. I hope this interview article will cheer up someone and trigger a change."

After working for several international companies including McKinsey and JPMorgan, Katsuma has been working as an economic commentator.

Acceptance of same-sex unions has begun to spread slowly in Japan, although legal marriage remains limited to a union of man and woman.

In April, the city government of Fukuoka began recognizing partnerships of LGBT couples, adding to efforts to eliminate discrimination against sexual minorities.

The city in southwestern Japan became the seventh municipality in the country to begin recognizing such unions, thereby conferring various rights and privileges to them, after Tokyo's Shibuya Ward became the first government to do so in 2015.

Katsuma's partner Masuhara received the first such certificate from Shibuya Ward when she registered her partnership with another woman. The couple later ended their relationship.

According to a survey conducted in 2015 by the Japanese advertising giant Dentsu Inc., one in 13 people is estimated to be a member of the country's LGBT community.