The United States is returning over 9,000 acres of land on Okinawa to the Japanese government, acreage it has held since the conclusion of World War II .

The move is the largest return of land since 1972 and comes amid long-standing controversy over the U.S. military presence on the southern Japanese island, heightened by a string of crimes that includes the murder of a 20-year-old Japanese woman earlier this year. A former U.S. Marine was arrested and charged in the case.

The handover reportedly reduces the amount of U.S.-controlled land on Okinawa by 17 percent, according to the U.S. military. Japanese Prime Minister Shinzo Abe and Caroline Kennedy, the U.S. ambassador to Japan, attended a Wednesday ceremony marking the transfer in Tokyo, with another event planned for Thursday on Okinawa.

But for some, the handover is not enough, especially since it comes with strings attached. According to CNN , the Japanese government in exchange agreed to build new helipads for U.S. military use on Okinawa, in line with the 1960 U.S.-Japan Treaty of Mutual Cooperation and Security that grants the U.S. the right to certain defense facilities.

There are approximately 50,000 U.S. military personnel in all of Japan. The crash of an Osprey aircraft near Okinawa earlier this month also has contributed to anti-U.S. military tensions.

"We feel betrayed by the [Japanese] government," Takashi Kishimoto, a spokesman for activist group Peace Okinawa, told CNN. "From our point of view, the U.S. military [is] giving back something [it doesn't] want while having new Osprey runways built.

"Okinawa alone is host to 74 percent of the U.S.' military bases in Japan," he said. "The return of this land only reduces this presence to 71 percent."

The New York Times reported in 2015 that Abe, seeking to position his country as Washington's most essential partner in Asia, has faced resistance from "a public that for decades has recoiled from anything resembling the militarism that led Japan into World War II."

"Prime Minister Abe wants to regain Japan's pride, but at the expense of Okinawa," Takeshi Onaga, the governor of Okinawa prefecture, said last year. "We are not going to take that lying down."

Opposition to the U.S. military presence on Okinawa has even spurred calls for Okinawan independence .