A group of residents of Okinawa Prefecture in Japan has launched an organization seeking the southern island’s independence.

Japanese media reported that the Okinawan independence activists named the organization after the island’s old name “Ryukyu.”

May 15th marks the 41st anniversary of Okinawa’s return to Japan from the U.S. that administered the island for 27 years under the Treaty of San Francisco, following the end of World War Two.

Okinawan people are calling for independence, complaining about Japan’s discriminatory treatment, such as the concentration of U.S. military bases on their island. Okinawa is home to 70 percent of U.S. bases on Japanese territory.