TOKYO -- Zhao Ruimin, a hard-faced and short-haired 28-year-old from the coal-mining country of China's hardscrabble Anhui province, fingered a 9-inch bandage on his right arm.
A few days earlier, three Japanese workers had caught him in the wee hours of a Friday morning after he arrived for his day as a laborer at Tokyo's Tsukiji Fish Market.
They dragged him down a narrow aisle between still-empty BTC seafood stalls until they felt sure they were out of sight and earshot of supervisors, then pummeled him for several minutes.
The beating was punctuated by repeated shouts, but Mr. Zhao understood only two sentences. He had heard the words before -- "Go away, foreigner!" and "Stop stealing Japanese jobs!"
Mr. Zhao's beating was one of several that Chinese workers say they have received at the fish market in the past year.
The fights at Tsukiji are in turn part of steadily rising tensions between Asian foreigners and Japanese whose jobs are at the bottom end of the labor scale in the world's second-biggest economy.
"Japanese have always had an island mentality," a U.S. diplomat said. "They assumed that because the Sea of Japan is wider than the Rio Grande, they wouldn't have this problem. But illegal immigrants are becoming a small and shifting but permanent subclass in Japanese society.
"It's a problem the Japanese don't want to acknowledge, and anyway they have no political or economic voice," she added. "So the law and the bureaucracy look upon it as an enforcement problem rather than a social issue."
More than four decades of seldom-interrupted economic boom times have created a labor shortage that makes Japan an irresistible magnet for foreign workers.
Employers of illegal foreign workers range from factory owners and office managers to bar operators and married couples offering housekeeping jobs that few young Japanese are willing to take.
They find workers by advertising in South and Southeast Asian newspapers and by patronizing growing ranks of employment agencies that specialize in foreign workers.
Both legal and illegal Asian immigrants continue to flock here in steadily increasing tens of thousands, undeterred by beatings, sporadic arrest and deportation campaigns, squalid living conditions, widely publicized abuse by employers and well-known gangster schemes to lure them or pressure them into drugs, crime and prostitution.
Distaste and sometimes anger over the growing presence of Asian foreign laborers is a steady theme of letters to newspapers and talk shows, and it is working its way into political campaigns.
But labor laws and immigration rules have failed to keep pace with social and economic change, often leaving the foreign workers exposed to rampant exploitation and sometimes physical abuse by employers, landlords, employment agents and fellow workers.
The Immigration Bureau of the Department of Justice has found more than 20,000 foreigners in violation of immigration laws or rules in each of the last three years, a huge leap from the early 1980s, before the overheated economy began to create big increases in the numbers of Asian workers here legally and illegally.
The overwhelming majority of those violations -- usually about 80 percent or more -- consist of taking jobs that violate the terms of a visa.
Nobody has a clear idea how many illegal workers there may be, but lawyers, union leaders and charity workers all say the Immigration Bureau's usual estimate of about 100,000 to 120,000 accounts for a fraction of the actual number.
Even several times that number would be less than 1 percent of the country's population, but for many Japanese, seeing poorer Asian foreigners in groups on the street and at work sites is a new and shocking experience.
The only comparable experience has been with tens of thousands of Koreans brought here as forced laborers before World War II, when Korea was a Japanese colony.
Under Japanese laws, most of those Koreans' 700,000 descendants are still not citizens even though they and their parents may have been born here.
For the Asian workers, the attraction is the obvious one of money, since even bottom-end Japanese jobs give them a chance to send home sums seldom seen in their own countries -- and in hard currency.
For Japanese employers, the attraction very often is the vulnerable position in which low-paid foreign workers find themselves almost upon arrival under Japan's hard-line immigration laws and hard-to-use labor laws.
Mr. Zhao, for example, accepted his beating quietly rather than report it to the police or his bosses.
"I told my boss I bumped into another worker's handcart and fell down," he said. "If I told him anything that brought any officials in, maybe the immigration people would find out I'm working more than 20 hours a week."
Like 30,000 other Chinese, Mr. Zhao is in Japan on a student visa that forbids him to work more than 20 hours a week.
Because of that visa limitation, his name has been changed for this article.