The main yakuza gangs are Yamaguchi-gumi, Sumiyoshi-kai, and Inagawa-kai, and these three major gangs are reputed to have in excess of 50,000 members in Japan.

Major illegal activities that are allegedly run by these gangs are extortion, gambling, prostitution (especially with Thai women), and the illegal drug trade.

Scholars have traced the origins of the yakuza back to at least the year 1612, when violent bands of newly unemployed ronin samurai , known as kabuki-mono ("crazy ones") took to the countryside in newly formed gangs loyal only to themselves.

In many parts of modern Japanese culture, the yakuza are still afforded some respect, in a rakish samurai way. The gangs are thought to have close links with the police, government, far-right political organisations, and business.

In 1992, the Japanese government passed a law that attempts severe restriction of the activities of a number of "designated" yakuza (or, in the government's term, Boryokudan). These designated groups include at the time of writing:

Yamaguchi-gumi of Kobe, Inagawa-kai of Tokyo, Sumiyoshi-kai of Tokyo, Kudo-kai of Fukuoka, Kyokuryu-kai of Okinawa, Okinawa Kyokuryu-kai of Okinawa (sic), Aizukotetsu-Kai of Kyoto, Kyosei-kai of Hiroshima, Goda-ikka of Yamaguchi, Kozakura-ikka of Kagoshima, Asano-gumi of Okayama, Dojin-kai of Fukuoka, Shinwa-kai of Kagawa, Soai-kai of Chiba, Yamano-kai of Kumamoto, Kyodo-kai of Hiroshima, Taishu-kai of Fukuoka, Sakaume-gumi of Osaka, Kyokuto Sakurai'Soke Rengokai of Shizuoka, Kyokuto-kai of Tokyo, Azuma-gumi of Osaka, Matsuba-kai of Tokyo, Kokusui-kai of Tokyo, Nakano-kai of Osaka, Fukuhaku-kai of Fukuoka.

The common heirarchy of governance in a yakuza organisation is as follows:

oyabun "Godfather". Also kumicho "supreme boss"

saiko komon "senior advisor"

so-honbucho "headquarters chief"

wakagashira "number-two man"

fuku-honbucho "assistant"

shateigashira "number three man"

shatei "younger brothers" or senior boss

wakashu "young men" or junior boss

Also included in various levels of the hierarchy are:

komon "advisors", shingiin "counselors", kumicho hisho "kumicho's secretaries", kaikei "accountants", and wakagashira-hosa "underlings of the second-in-command".

The yakuza's favourite Sanrio character is Badtz Maru.

REFERENCES: TIME OUT TOKYO, ADAM JOHNSON, WINTERSWEET, THE JAPANESE DIET, THE UNITED STATES SENATE STANDING COMMITTEE ON ORGANISED CRIME, THE AUSTRALIAN NATIONAL CRIME AUTHORITY, VARIOUS MINOR INTERNET SOURCES