Image copyright Mike Sunda Image caption Abattoir workers at the Shibaura meat market

Japan has a reputation of being a homogeneous, mostly harmonious society. There are few foreigners, linguistic differences are rare and on the surface class distinctions are largely absent. But, as Mike Sunda discovered, there is one, often hidden, exception: Japan's untouchables.

In the corner of a pristine room tucked away in Tokyo's Shibaura meat market is a table topped with a stack of crudely composed hate mail - evidence of a prejudice that dates back to medieval times.

Slaughtermen, undertakers, those working with leather and in other "unclean" professions such as sanitation have long been marginalised in Japan. That prejudice continues to this day and especially for those working in the Shibaura abattoir.

Never mind that the men here are dicing up some of the most expensive and highly prized animals on the planet. This is where Japan's world famous wagyu beef is prepared - prime steaks, shot through with ribbons of fat, that can set you back eye-watering prices.

Image copyright Mike sunda Image caption One of the hate mail letters received by abattoir workers

It's a process requiring such immense skill, training and mental fortitude that mastering the job can take a decade. And yet, for all the craftsmanship that goes into their work, many here will never speak freely about their occupation.

"When people ask us about what sort of work we do, we hesitate over how to answer," slaughterman Yuki Miyazaki says.

"In most cases, it's because we don't want our families to get hurt. If it's us facing discrimination, we can fight against that. But if our children are discriminated against, they don't have the power to fight back. We have to protect them."

Feudal origins

Like many in the abattoir because of his profession, Miyazaki is associated with the Burakumin, Japan's "untouchable" class.

Burakumin, meaning "hamlet people", dates back to the feudal era. It originally referred to the segregated communities made up of labourers working in occupations that were considered impure or tainted by death, such as executioners, butchers and undertakers.

The lowest of these outcasts, known as Eta, meaning "abundance of filth", could be killed with impunity by members of the Samurai if they had committed a crime. As recently as the mid-19th Century a magistrate is recorded as declaring that "an Eta is worth one seventh of an ordinary person".

Though generally considered offensive, the term Eta is still in use today. One of the letters received at the abattoir expresses sympathy for the animals being killed "as they're being killed by Eta."

The caste system was abolished in 1871 along with the feudal system. Yet barriers to their integration remained. Marginalised Burakumin communities were widespread across Japan.

Having the wrong address on your family registry, which records birthplace and is often requested by employers, often led to discrimination.

Efforts were made in the 1960s to improve their lot by funding assimilation projects that improved housing and raise living standards, but despite this discrimination continued..

Blacklist

In the mid-1970s, a Buraku rights group discovered the existence of a 330-page handwritten list of Buraku names and community locations that was being sold secretly to employers by mail order.

Many big name Japanese firms were using the list to screen job applicants.

As recently as 2009, there was public outcry when Google Earth incorporated publicly available historical maps of Tokyo and Osaka that pinpointed the location of Buraku villages in feudal times, dragging up the contentious issues of prejudice and profiling.

Image copyright Getty Images Image caption Members of of Japan's largest organised crime syndicate, the Yamaguchi-gumi, said to count many Burakumin among its ranks.

Today, the exact number of people living in historic Buraku communities is hard to pin down.

A government survey in 1993, listed nearly a million people living in more than 4,000 communities around the country. The Burakumin Liberation League (BLL), a rights organisation founded in 1955, puts the number of communities at around 6,000 and estimates that the total number of Burakumin is closer to three million.

Toshikazu Kondo, from the BLL, says they still encounter such lists today, but find that they are being used for different purposes.

"When it was discovered in the 1970s that corporations were using these lists to conduct background checks on potential recruits, regulations were brought up to make that illegal," he says.

"Nowadays it's still a well-known fact that people are buying this information, but rather than corporations, it's individuals buying it to check on future in-laws ahead of marriage. That's one of the biggest examples of discrimination that we frequently face."

The mob connection

In a survey last year conducted by the Tokyo government, one in 10 said that they would have reservations about their child marrying someone with Burakumin ancestry, although nearly a half of respondents said this wouldn't bother them.

One reason for the lingering stigma may be the association of Buraku communities with the yakuza, the Japanese mob.

Jake Adelstein, an American reporter who has worked the Japanese crime beat for 20 years, estimates that a third of yakuza come from Buraku communities, drawn to the organization when other doors were closed to them.

A yakuza leader justified his organisation to Adelstein on the basis that it gave people who had suffered discrimination a family and discipline.

"It's true - the yakuza is a meritocracy," Adelstein says. "If you are willing to be ruthless and a bully and pledge your loyalty to your boss, they'll take you."

However, it's not just those with Burakumin ancestry that run the risk of prejudice. So strong is the historic connection between certain jobs and this historical category of outcasts that all workers at the slaughterhouse run the risk of discrimination, no matter their family history.

Beer snub

Yutaka Tochigi, the 58-year-old president of the Shibaura Slaughterhouse Union left his job as a computer programmer to spend more time with his children but immediately ran into opposition from his family.

"My father said to me that I might as well be pumping septic tanks. I realised that he meant I was doing a Burakumin job," says Tochigi, who doesn't have Burakumin ancestry.

"I remember once when my wife and I were visiting with some of her father's relatives. When I told them what I did, they stopped pouring me beer."

Image copyright Mike Sunda Image caption Yutaka Tochigi, president of the Shibaura Slaughterhouse Union

Both Tochigi, and the BLL's Kondo are, however, hopeful that things are changing for the better.

"You don't see as much hate speech as before - and those who have attempted it have been forced to pay damages in court cases," Kondo says.

"We still hear about workplace discrimination and anti-Burakumin graffiti, but more than ever before there are people getting in touch to inform us when this happens."

The small room which contains the table display of hate mail is part of the Shibaura meat market's information centre, an educational outreach effort to try and change attitudes.

Just next to the table, on a wall, are letters of another kind. Grateful messages from groups of schoolchildren brought in on tours to learn about the remarkable skill and dedication with which the labourers carry out their jobs - evidence, perhaps, that old, discriminatory habits may yet be consigned to history.

About the author: Mike Sunda is a Tokyo-based writer specialising in music and Japanese youth and urban culture.

Additional reporting by Rebecca Milner.