A daughter’s engagement is a time of joy for any proud father.

Not so for Ikuo Aoki: His daughter was thrown out of her boyfriend’s family home when the young couple went there to announce their plans to marry.

The reason was unstated but well-understood — Aoki is a descendant of Japan’s former “burakumin” outcast class, a distinction that has brought his family a lifetime of ridicule, discrimination and abuse.

“I almost rushed over to their house to condemn them, but I didn’t because her boyfriend was still considering marrying her,” said Aoki, 68. His restraint made no difference; the couple eventually broke up.

Ethnically identical to other Japanese, the burakumin suffered for centuries at the bottom of the feudal hierarchy, digging graves, chopping meat and performing other jobs associated under Buddhism and the native Shinto religion with the impurities of death.

In recent decades, the former untouchables have made vast strides. Slums have been cleaned up, education levels have risen and many burakumin descendants have quietly blended into the rest of society.

But more than a century after Japan’s caste system was abolished in 1871, they still face the injustice of bigotry: scuttled marriage engagements, the taunts of strangers and rejected job applications.

“There has been some progress,” said Takao Yoshida of the Buraku Liberation League, Japan’s largest outcast rights group. “But you face discrimination whenever you’re at life’s turning points, such as marriage and employment. You just can’t avoid it.”

Known in the feudal period as either “filth” or “nonhuman,” the outcasts were legally trapped below the warrior, artisan, farmer and merchant classes, which were themselves ranked in this descending order. The burakumin had to follow a dress code and were restricted to living in special hamlets.

Even after the caste system was outlawed, bias kept burakumin largely confined to their villages, and they were easily singled out for abuse, based on address.

It still happens. Japan’s enduring family registry system — which keeps a file on every Japanese citizen’s background going back generations — means that potential marriage partners or employers have a way of uncovering burakumin origins.

Such discoveries have torpedoed many marriages and job applications, according to activists.

“We have the same skin color and we speak the same language, so the burakumin discrimination is difficult to understand from outside Japan,” said Satoshi Uesugi, a historian at Kansai University in Osaka. “It’s because Japanese judge others by bloodline and birthplace.”

According to a government survey conducted in 1993, about 900,000 Japanese with burakumin background lived in 4,442 ancestral villages nationwide. Rights groups say 2 million others now live outside their hamlets.

Following decades of civil rights protests, the government enacted integration laws in 1969 aimed at improving living conditions in the hamlets. The projects upgraded housing, roads and education until 2002, when the government said it had done enough.

Burakumin descendants say there is more work to do. In a society that puts a premium on conformity, the stigma of being in a community that lived apart from — and below — the Japanese mainstream for centuries has been hard to erase.

Fear of being tainted by this stigma has led detective agencies to compile lists of burakumin descendants that families can use to screen their children’s proposed marriage partners, or for businesses to check the pedigree of job applicants.

A case in which a company was accused of purchasing such a list in 1998 in Osaka — home to a large number of burakumin descendants — prompted an investigation by rights groups and local authorities. Activists, however, say these lists are still in circulation, some on the Internet.

The discrimination has an economic impact as well.

A recent survey conducted by an activist group showed that unemployment in their communities was roughly twice the national average of about 5 percent. Students of buraku descent advance to higher education at only 60 percent of the national average.

The economic dimension of discrimination has taken on greater importance over the past decade as Japan’s finances have faltered.

“When economy and labor conditions improve elsewhere, the effect reaches us much later,” said Buraku Liberation League President Shigeyuki Kumisaka. “Many of us work at small companies and our living conditions are still very vulnerable.”

Then there’s just plain harassment — something Aoki has known all his life.

When Aoki was a child, his parents moved regularly, changing their registered address in an effort to hide their identity. Even today, he gets harassment letters that spew hatred and abuse on a daily basis.

“You nonhumans from the hamlets have blood that is vulgar and tainted,” reads one of the letters sent to Aoki, who said the missives are sometimes intentionally sent to his neighbors to embarrass him.

Even though he’s an activist for the rights of burakumin descendants, he refused to reveal his daughter’s name for fear she would suffer from the exposure.

“You never know what could happen to her,” Aoki said. “I’ve got to be very careful about my daughter.”