Japan has lodged a strong protest with the United States after a US Marine was arrested on suspicion of robbing and killing a local woman in Okinawa, an incident that has renewed concerns over crimes involving US military personnel stationed on the island.

Japanese Prime Minister Sanae Takaichi, speaking to parliament in Tokyo on the first day of an extraordinary Diet session, said Japan has called for full US cooperation with the investigation, stricter discipline among US military personnel and thorough measures to prevent similar incidents.

The suspect, 20-year-old US Marine Devin Ballard, stationed in Okinawa, was taken into custody and sent to prosecutors, according to Okinawa police. He is suspected of robbing and murdering 39-year-old local resident Anna Yagi at a hotel in the prefectural capital, Naha, in the early hours of Saturday, October 3.

Ballard has denied the allegations, according to police.

The incident has drawn anger in Japan from both the government and the public.

The day after the incident, Japanese Foreign Minister Toshimitsu Motegi and Defense Minister Shinjiro Koizumi summoned US Ambassador to Japan George Glass and Commander of US Forces Japan Stephen Jost, respectively, to lodge strong protests, urging the US military to strengthen discipline and take measures to prevent similar cases.

Chief Cabinet Secretary Minoru Kihara said Monday that Japan will "continue to urge the US side to thoroughly enforce discipline."

A protest also took place outside the prime minister's official residence in Tokyo on Monday night. Some demonstrators linked the incident to the long history of sexual violence involving US military personnel in Okinawa and criticized what they called the Japanese government's inadequate response.

Mizuho Fukushima, a member of Japan's House of Councillors, criticized the Japan-US Status of Forces Agreement, arguing that its custody provisions hamper Japanese investigations of US military personnel suspected of crimes.

Crimes involving US military personnel have long been contentious in Okinawa. According to official statistics, Okinawa prefectural police recorded 101 criminal cases involving US military personnel, civilian employees and their family members in 2025, the first time the annual figure had exceeded 100 since 2003.