The monument has stood in San Francisco for a year. It depicts young women from Korea, China and the Philippines standing on a pedestal holding hands, while a statue of Kim Hak-sun, a Korean activist, gazes up at them.

But the view from Osaka, Japan, of the memorial, which commemorates the tens of thousands of “comfort women” who were detained and raped by Japanese soldiers before and during World War II, has been critical. This week, the controversy boiled over as Osaka officially severed its sister-city partnership with San Francisco.

In a letter dated Tuesday, Osaka’s mayor, Hirofumi Yoshimura, followed through on a threat issued a year ago to end his city’s longstanding relationship with San Francisco in protest of the monument, saying it presented a one-sided message.

“I earnestly request that you promptly remove” the memorial and an accompanying plaque “without further delay,” Mr. Yoshimura wrote, according to an emailed copy of the letter. He added that he would revive ties with San Francisco if they were removed from city property.