There are some strange superstitions w.r.t. death in Japanese culture. In Japanese the number 4 sounds sort of like death so it's a number they avoid a lot (it's missing from many elevator options, similar to how 13 is skipped sometimes) and patterns of squares are sometimes avoided to prevent having 4 corners meet (especially with straw mats).
I had never heard of this, though. The class of untouchables who work close to death. Really interesting stuff.
As other comments pointed, this caste system itself isn't really a "secret". We learn in school that it had existed, and there are quite a few stories dealing with it (A novel "The Broken Commandment" (破戒) by Touson Shimazaki, and an epic manga series "Kamui" (カムイ伝) are among the best ones; both have been translated to English).
However, things got complicated in modern society; officially the government denies the discrimination exist; some people still keeps prejudice; and the topic is used as a political tool.
"Based on records of buildings with Otis brand elevators, as many as 85 percent of the high rises in the world don't have a 13th floor, says Dilip Rangnekar, spokesman for the Farmington, CT-based elevator maker."
- http://realtytimes.com/todaysheadlines1/item/15685-20020913_...
Superstitions are alive and well around the world. In the U.S., the number of people who still turn to astrology when it comes explaining success or failure in dating and relationships will astound you. Even in places like New York City.
In reply to tsotha, 1801 Century Park East, Los Angeles, CA 90067 is an example. At least it was when I worked there after law school (ahem some time ago).
I had never heard of this, though. The class of untouchables who work close to death. Really interesting stuff.