A US Marine has been arrested on suspicion of killing and robbing a woman in Okinawa, Japanese authorities have said.

The victim, identified as Anna Yagi, 39, was found dead in a hotel room in Naha, the prefectural capital, on Saturday. Okinawa is home to several major American military installations and tens of thousands of US service members.

Lance Corporal Devin Jacob Ballard, 20, who is stationed at Marine Corps Air Station Futenma in Ginowan, is accused of strangling Yagi and stealing her wallet and backpack. He has denied the allegations.

Surveillance footage reportedly showed a man believed to be Ballard entering the hotel with Yagi and later leaving alone with what appeared to be her belongings. Police located him in an entertainment district late Saturday.

The Marine Corps confirmed that Ballard is assigned to the III Marine Expeditionary Force and said it was cooperating with Japanese authorities.

“The case deals a major shock and adds fear to the Okinawans who have already been forced to live next to US bases,” newly elected Okinawa Governor Genta Koja told reporters. “It is absolutely unforgivable, and we are outraged.”

“I must say, discipline and troop education are not working at all,” he added, referring to measures introduced by the US military following a series of sexual assault cases involving American personnel on the island.

The Japanese government lodged a formal protest with Washington on Sunday. Prime Minister Sanae Takaichi demanded full cooperation with the investigation, stricter discipline among American personnel, and “thorough measures” to prevent similar incidents.

“The occurrence of such an extremely brutal and heinous incident is a matter of profound regret,” she wrote on X, extending sympathy to the victim’s family.

Foreign Minister Toshimitsu Motegi summoned US Ambassador George Glass, who pledged full cooperation with the investigation.

Okinawa accounts for just 0.6% of Japan’s territory but hosts 70.3% of the land area of US military facilities in Japan that are exclusively used by American forces, according to the Okinawa prefectural government.

Concerns over crime, aircraft noise, and pollution have fueled longstanding opposition to the bases. The 1995 abduction and rape of a 12-year-old girl by three US servicemen sparked mass protests. Demonstrations against the US military presence have continued, with a 2018 rally drawing an estimated 70,000 people.

In June 2024, Tokyo formally protested two alleged sexual assaults involving American personnel and delays in disclosing the cases. The Marine Corps subsequently stepped up sobriety checks and off-base patrols, while US Forces Japan later barred service members from off-base drinking establishments between 1 a.m. and 5 a.m.

Despite those measures, further sexual assault allegations involving American personnel followed. In January 2025, then-Chief Cabinet Secretary Yoshimasa Hayashi urged US Forces Japan to tighten discipline and take stronger measures to prevent further incidents.