This is a shocking entry in Wikipedia, but it shows how far racists will go to ensure that they can continue to segregate. In Japan, there are people who were once "outcasts" before the late 1800s Meiji Restoration. They are called "Buraku", and they are physically indistinguishable from other ethnic Japanese. Caste discrimination was outlawed, but, some people got it together to maintain a directory of all the people who were "outcast":

In November 1975, the Osaka branch of the Buraku Liberation League was tipped off about the existence of a book called "A Comprehensive List of Buraku Area Names" (特殊部落地名総鑑 Tokushu Buraku Chimei Soukan). Investigations revealed that copies of the hand-written 330-page book were being secretly sold by an Osaka-based firm to numerous firms and individuals throughout Japan by a mail order service called Cablenet, at between ¥5,000 and ¥50,000 per copy.

The book contained a nationwide list of all the names and locations of buraku settlements (as well as the primary means of employment of their inhabitants), which could be compared against an individual's address to determine if they were buraku residents.

The preface contained the following message: "At this time, we have decided to go against public opinion and create this book [for] personnel managers grappling with employment issues, and families pained by problems with their children's marriages."

More than 200 large Japanese firms, including (according to the Buraku Liberation and Human Rights Research Centre of Osaka) Toyota, Nissan, Honda and Daihatsu, along with thousands of individuals purchased copies of the book.

In 1985, partially in response to the popularity of this book, and an increase in mimoto chōsa (身元調査, private investigation into one's background) the Osaka prefectural government introduced "An Ordinance to Regulate Personal Background Investigation Conducive to Buraku Discrimination".

Although the production and sale of the book has been banned, numerous copies of it are still in existence, and in 1997, an Osaka private investigation firm was the first to be charged with violation of the 1985 statute for using the text. It is not unlikely that more of Japan's highly-lucrative private investigation market still enjoy ownership and use of the book.

That is evil and undemocratic.

See: Burakumin in Wikipedia

Now, what's interesting is this other page, about Buraku kingpins. The comments lay some interesting information out.

Buraku Biggest Taboo

So the situation is lousy, You have all this discrimination, and then multiple layers of it, so the gangs are going after the indigenous, and the gangs are full of outcasts. On top of them are cops and semi-outcasts. And on top of them are the Japanese, who are really mostly descendents of colonists from China, or think they are.

Also: Buraku Liberation League, the leading human rights group representing the oppressed people.