FILE - Japan's student protesters stone at riot police, background, during an "Okinawa Day" demonstration against U.S. control over Okinawa and the U.S.-Japan security treaty, near Tokyo's Shimbashi railway station on April 28, 1969. Okinawa on Sunday, May 15, 2022, marks the 50th anniversary of its return to Japan on May 15, 1972, which ended 27 years of U.S. rule after one of the bloodiest battles of World War II was fought on the southern Japanese island. (AP Photo/Koichiro Morita, File)