Story highlights Hwang Keum-ja died in South Korea, one of the dwindling number of "comfort women"

Japan forced 200,000 women into sex slavery to service WWII Japanese soldiers

Japan has formally apologized for atrocities against "comfort women"

Another voice that could have told about the horrors of being a "comfort woman" -- a sex slave used by Japanese soldiers during World War II -- has fallen silent, according to South Korean authorities.

Hwang Keum-ja, 89, died of lung and respiratory disease at a hospital in Seoul Sunday.

Cho Yoon-sun, South Korea's Minister of Gender and Equality and Family, said she had been attempting to meet each of her country's surviving comfort women individually, but had not yet visited Hwang.

"My heart is aching as she died before I was able to meet her," she said in a statement, praising Hwang for her efforts to support others despite the hardships she faced, and vowing that her government would deliver greater support to other comfort women.

Japan forced about 200,000 women into sex slavery, luring them to "comfort stations" set up throughout East Asia by the Japanese military from 1932 until the end of the war, according to nonprofit advocacy group Washington Coalition for Comfort Women Issues . Mostly Korean, the women were lied to and told they would get jobs if they went to the brothels, the center says.

CNN has widely reported on the stories of the women. Many have said they were kidnapped. For resisting sex, some say, they were raped and beaten.

Hwang Keum-ja was forced to work at a glass factory at 13 and then sent to China to work as a sex slave at 16, South Korea's state news agency Yonhap reported. After Korea was freed from Japanese occupation in 1945, she went home and lived the rest of her life alone, the agency said. She worked as a garbage collector, but didn't make enough, so she had to rely on government subsidies.

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It's unclear how, but she was able to make three donations to a scholarship fund totaling more than $92,000, which helped earn her an award for her generosity in 2011 in Korea, Yonhap said. Hwang's dying wish was that all her assets be donated to charity.

She had one adopted son, according to the ministry.

The Japanese Ministry of Foreign Affairs states: "Japan has extended its sincere apologies and remorse to all those women on various occasions such as an apology statement by the Chief Cabinet Secretary Yohei Kono in 1993." The country has helped establish the Asian Women's Fund in 1995, which is supported by government funds and provides assistance to former comfort women.

The South Korean government however does not believe this is enough. Along with the surviving comfort women it is calling for an official government apology, acknowledging legal responsibility for the crimes. Seoul wants Tokyo to provide direct compensation to the victims.

But Japan has resisted direct payments to the victims, prompting activists and former comfort women to say leaders are avoiding officially acknowledging what happened.

In 2013, the mayor of Osaka, Japan, stirred fierce controversy when he told reporters that "anyone would understand" the role of "comfort women" when soldiers were risking their lives and deserved a "rest." Toru Hashimoto said the use of the women was "necessary."

Though he acknowledged the issue was a "tragic result of war," Hashimoto insisted that soldiers using the women wasn't unique to Japan.

Hashimoto also revealed that he told a U.S. military commander during a trip to a base on the island of Okinawa that U.S. personnel should "utilize more" the adult entertainment business in Japan.

South Korea has urged Japan to resolve the issue directly with victims, noting that time is running out because most of them are elderly and dying.

Hwang's death brings the total number of living South Korean victims of the comfort women sex slavery circuit in South Korea down to 55, 5 of whom live abroad.