Business is slow in Okinawa’s biggest red-light district. Touts stand idle beneath neon signs advertising “soap-land” brothels, where prostitutes lather male clients for money. A handful of men loiter to peer at the photos of women pasted on billboards outside, though few appear willing to part with Y15,000 (£100) to spend an hour with one inside. Desperate as some of the businesses are, however, many still decline one type of customer: US military servicemen.

“Too much trouble,” explains one tout working the Tsuji-machi district of Naha, Okinawa’s capital. The soap-land businesses that do admit Americans tend to pair them with older, more experienced women. “They scare the younger girls,” says another tout. “Especially when they have had a few drinks.”

Okinawa has lived uneasily for decades with its huge American military presence. US bases occupy nearly 20 per cent of the crowded main island of Japan’s southernmost prefecture, as part of Tokyo’s half-century alliance with Washington. The US maintains 14 military installations on Okinawa housing roughly 25,000 men and women – the Marine Corps Northern Training Area alone occupies close to 40 square miles, and includes the world’s only jungle warfare training centre.

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The controversies associated with such a huge deployment are legion; in 1969, shortly after the start of the Vietnam war, 13,000 tons of poison gas including sarin and VX leaked from a storage base in Okinawa, causing residents to be evacuated and environmental damage that prevailed for years. There have also been a series of recent allegations that Agent Orange was extensively stored there – claims that the US military has denied, following its own internal investigations.

Pilots, sailors and often traumatised young marines rotate through the area every year from war zones in Afghanistan and the Middle East. Over the years they have racked up thousands of crimes, including a number of rapes that have caused outrage and triggered a fierce and increasingly uncompromising anti-base movement.

In the most notorious case, three US military personnel took turns raping a 12-year-old local girl on a deserted Okinawan beach in 1995. The men had debated paying for a prostitute before concluding it was too expensive and abducting their victim instead. They later fled back to base, leaving her to die. “The American military on Okinawa has never recovered,” says Doug Lummis, a former US Marine turned political scientist. In an attempt to ease the tensions, thousands of US marines will soon be moved to a base in Guam.

One of Japan’s leading politicians stumbled into the political minefield in April when he off-handedly told a US military commander on Okinawa that “hot-blooded” American soldiers should use “legal adult entertainment” to control their sexual urges. Toru Hashimoto, who is mayor of Osaka and co-leader of the Japan Restoration Party, told the reportedly stunned commander that soldiers everywhere “are put in extreme situations in which they can lose their lives,” so they are “naturally overflowing with energy”.

“We have to think about the way they can let it out somewhere,” he said. Okinawans reacted with fury. A federation of local women’s groups said Mr Hashimoto managed to insult not just women, but men, by assuming that they can’t survive without such disfigured sex. The National Federation of Regional Women’s Organisations said the argument that men can’t control their sexual urges was a “lie used to justify rape.”

The subsequent uproar forced Mr Hashimoto last month to apologise for the comments, which he linked to Japan’s involvement in herding an estimated 200,000 Asian women into wartime military brothels. But he argued the Japanese army was not unique. “All countries” should look squarely at their past, he said, citing Britain, the US, France and Russia for indulging in what he jarringly called “sex on the battlefield.”

A populist right-winger, Mr Hashimoto tapped into a vein of anger at the US military presence on Okinawa. “Every time a crime has occurred,” he said, the Americans promise it will never happen again. Nevertheless, these crimes have not stopped.” A few months before he spoke, Naha district court sent two US sailors to jail for gang-raping an Okinawan woman on her way home from work. After the assault, the men bought drinks in a bar with the Y7,000 they stole from their victim.

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“We’ve been living with military crimes since 1945,” says Chuuji Chinen, a retired journalist who campaigns against the US bases. “If (Hashimoto) is concerned about us he should tell the soldiers to get out instead of asking local women to service them.”

Pressure on Washington to rein in sex crimes by the military has been building. President Barack Obama recently called the issue a national security problem after a Pentagon report estimated there were 26,000 sexual assaults inside the US armed forces last year. Experts say that dwarfs military-on-civilian crimes around the roughly 1,000 US bases dotted across the world, some close to the planet’s most notorious fleshpots. In response, military commanders have been ordered to tighten discipline and crack down on misconduct.

On Okinawa, potentially one of the most politically explosive American hosts, troops are increasingly confined to base. When they venture off, they are allowed to consume just two alcoholic drinks, with a meal, and they must be back at 10pm – recognition that booze, late nights and young soldiers are a potentially lethal mix. Many servicemen reportedly resent the restrictions but accept them because the situation on the main island has grown so tense.

“From a leadership standpoint it makes sense because it’s a political game,” says Rich Krawczyk, an American engineer based in Kadena, the largest US airbase in Asia. Last year, the Kadena base commander warned personnel to stay out of another local red-light area called Yoshihara. “The solicitation of prostitutes violates the basic principles of human rights and decency every Marine has vowed to defend as integral to their service,” says military spokesman First Lieutenant Evan A Almaas.

Critics say that warning was more about politics than morals. Many local sex businesses have stopped serving them. “The only reason why some “soaps” accept American military personnel is because there are too few customers,” says a prostitute in Tsuji-machi who requested anonymity. She says she’ll have sex with older men during the day time but refuses younger troops at night.

“They get rough, grabbing you by the neck and slapping your face,” she says. “I’d prefer not to work at all than endure that. Why should we have to absorb the hatred in the world?”