Takaichi described the killing as a “heinous” crime in parliament and called on US military authorities to “thoroughly enforce discipline” among American servicemen stationed in Japan.

The 20-year-old Marine, Devin Ballard, was arrested on suspicion of strangling Anna Yagi, 39, at a hotel in Naha, the capital of Okinawa, police said.

Ballard is also suspected of stealing Yagi’s wallet and backpack and has denied the allegations.

The arrest has triggered renewed anger on Okinawa, where the heavy US military presence has remained a deep source of tension and resentment among local residents.

Okinawa hosts the majority of US forces and about 70% of Japan’s US military facilities, despite accounting for only a small share of Japan’s territory.

Takaichi told lawmakers on Monday that Japan had urged the US to provide “full cooperation with the investigation” and called for “strict discipline among US military personnel”.

Separately, Genta Koja, a pro-US base governor backed by Takaichi’s Liberal Democratic party, described the arrest as a “major shock” to Okinawa and said it “raises fears among Okinawans who have already been forced to live next to US bases”.

“It is absolutely unforgivable, and we are outraged,” Koja said.

He said the case demonstrated that US efforts to improve discipline among its troops had failed.

“I’m enraged by the loss of a precious life of an Okinawan resident,” Koja told Lt Gen Benjamin Watson, commander of III Marine Expeditionary Force, and the US consul general in Naha, Andrew Ou, after Ballard’s arrest.

Watson acknowledged the anger and concern caused by the case, saying it had caused “significant concern and anxiety among the residents of Okinawa, our neighbours”.

“We are committed to being good neighbours … and earning the trust of the Okinawan people,” he added.

The latest case has also reopened painful memories of earlier crimes involving US servicemen, including the 1995 rape of a 12-year-old girl by three American servicemen.

The crime triggered intense anti-US sentiment on Okinawa and was followed by an agreement between Tokyo and Washington to reduce the US military footprint by closing Futenma and relocating its functions to Henoko on the island’s northeastern coast.

Anger erupted again in 2024 after the rape of a teenage girl by a US service member and the delayed disclosure of the crime.

Crimes involving US troops on Okinawa have increased in recent years, rising from about 40 in 2020 to 101 last year, according to prefectural police.

Meanwhile, the latest killing has further intensified opposition to the continued US military presence on an island that has borne a disproportionate share of the burden of the Japan-US military alliance.

The planned relocation of Futenma air station, where Ballard is stationed, has remained stalled for decades amid opposition from residents near the proposed site and local politicians who want US military facilities removed from Okinawa altogether.

Koja’s election had raised hopes that Tokyo and Washington could finally make progress on transferring the Marine Corps base from a densely populated area to a remote offshore location.

The latest arrest, however, has once again placed the conduct of US troops and the cost of their presence at the center of public anger in Okinawa.

Under the Japan-US status of forces agreement, Ballard, who was arrested in a civilian district while off duty, will remain in Japanese custody.

Security footage showed him entering the hotel with Yagi and later leaving alone.

Kyodo News, citing police, reported that Yagi’s body was found in a hotel room and that she appeared to have been strangled.

Ballard was arrested by Japanese police on Sunday and sent to prosecutors on Monday, according to Kyodo News.

If convicted, he could face life imprisonment or the death penalty.

Yagi’s family said they were “devastated” by her death.

Her brother said in a statement: “Our parents are especially exhausted with grief after losing their daughter.”

About 54,000 US military personnel, including 18,000 Marines, are stationed in Japan, with the majority based in Okinawa.

The island remained under US administrative control after World War II before being returned to Japan in 1972.

Crimes including rape, assault, hit-and-run incidents and drink-driving involving US personnel have repeatedly sparked protests and fueled resentment toward the continued US military presence.