The statue “Women's Column of Strength” by artist Steven Whyte is displayed at St. Mary's Square on Nov. 1, 2017, in San Francisco. The statue has caused controversy since being installed in September by the Comfort Women Justice Coalition. (Justin Sullivan/Getty Images)

Japan's third-largest city, Osaka, and San Francisco became sister cities in 1957 — part of a project to twin Japanese cities with American counterparts to foster peace between former enemies and celebrate historical ties.

Sixty years later, that relationship is slated to come to an abrupt end. The cause of the breakup? A statue installed this year that commemorates the foreign “comfort women” forced to work in brothels by the Japanese army during World War II and the decades before.

The statue was unveiled in downtown San Francisco in late September to relatively little fanfare in the United States. But it has prompted dramatic headlines in Japan, with Osaka Mayor Hirofumi Yoshimura pledging Friday to end the sister city relationship after San Francisco officially designated the memorial city property this week.

“Our relationship of trust was completely destroyed,” Yoshimura said, according to the Asahi Shimbun. “I will dissolve the sister-city relationship.”

This is the only known footage of "comfort women" in existence. Historians estimate that as many as 200,000 women and girls from occupied countries like Korea, China and the Philippines were forced to work in brothels run by the Japanese Imperial Army during World War II. (Adam Taylor,Jason Aldag/The Washington Post)

The move signals how contentious the “comfort women” issue — and the statues commemorating them that have been spreading around the world — remains in Japan. Mainstream historians say that as many as 200,000 women and girls from occupied countries such as Korea, China and the Philippines were forced to work in brothels run by the Japanese army.

Osaka Mayor Hirofumi Yoshimura speaks at Osaka City Hall on Nov. 24. (Jiji Press/Agence France-Presse)

Though the issue was once rarely publicly acknowledged, after South Korean survivors of these brothels began to speak publicly in the 1990s, it was investigated and the ugly historical accounts gained legitimacy almost everywhere around the world.

Everywhere, that is, except Japan.

Though the Japanese government has made a number of gestures toward reconciliation — including a 1993 statement that offered “sincere apologies and remorse,” and a 2015 agreement with South Korea to “finally and irreversibly” put the issue behind them — right-wing Japanese groups say there is nothing to apologize for, while foreign critics contend that these measures have been weak.

Tensions over the installations of statues around the world to commemorate the issue have only compounded the problem. The first of these statues was installed in 2011 in South Korea, but they have since been installed in places such as Germany and Australia. There are reported to be 40 in South Korea and 10 in the United States, including in Virginia's Fairfax CountyNew Jersey and Southern California, though the San Francisco monument is the first in a major U.S. city.

The Japanese government has often responded angrily to the statues, arguing that it shouldn't be singled out for crimes that can be depressingly common during war. However, many experts have argued that this reaction has ended up causing larger problems for Japan's international interaction than the statues themselves.

“They have a strong sensitivity to how Japan is seen in the world. They see this as tarnishing Japan,” Jennifer Lind, author of “Sorry States: Apologies in International Politics” told The Washington Post this year. “[But] the more they try and squelch this? That's actually what ends up tarnishing Japan.”

When the San Francisco statue was announced last year, it sparked condemnation from Japan's Foreign Ministry, with a spokesman later saying that the action was “regrettable and incompatible with the position and efforts of the government of Japan.”

However, despite attempts to block the installation of the statue from the Japanese Consulate in San Francisco and a concerted email campaign from Japanese nationals, the statue was erected in St. Mary's Square on Sept. 23. The Asahi Shimbun reports that Yoshimura later asked San Francisco Mayor Edwin M. Lee for a meeting, but that the city declined the request by email Nov. 23, the day after Lee signed a resolution saying that the city accepted the statue.

At a news conference Friday, Japanese Chief Cabinet Secretary Yoshihide Suga said that the San Francisco statue and others like it were “extremely regrettable” and that Japan would “continue making every effort so that things like this won’t happen again.”

However, the activists behind San Francisco's statue have said that the response to its installation angered them. “I think it's a shame,” Julie Tang, a retired San Francisco Superior Court judge, told the San Francisco Chronicle on Friday. “They’re turning history on its head. Yoshimura is turning this into a geopolitical issue. It’s not. It’s a human rights issue. This is a global women’s issue to fight against sexual violence and using women as sex objects as a strategy of war.”

The Japan Times reports that some politicians in the Osaka city assembly also were concerned that Yoshimura's actions could harm the city's reputation abroad, and petitioned him to find a solution through dialogue.

Separately, Suga told reporters Friday that Japan had issued a protest after South Korea's Parliament passed a bill designating Aug. 14 as a day of commemoration for “comfort women.” Though Japan and South Korea had pledged to find a solution to their dispute over the issue in 2015, that agreement had quickly broken down, in part because of the disagreement about statues in Seoul and Busan.

Read more:

Why Japan is losing its battle against statues of colonial-era ‘comfort women’