In the real world, the Japanese organized crime community known as the Yakuza almost always go to a lot of trouble to cultivate the appearance of charitable, polite and reasonable businessmen. Since almost everybody does what that Yakuza members politely advise them to do, there is almost never any need for violence, and only a very small fraction of the Yakuza follow any kind of ultranationalist or other far-right ideology. Each Yakuza extended family has its leader, whose title is "Oyabun", or "elder brother," -- the same name is used to refer to the combat knife belonging to the character "47" in the Hitman franchise of games.
The term for the group itself derives from "ya-ku-sa", a losing combination of numbers rolled in gambling. This is left over from the fact in medieval times, Japan's military government tended to hire certain con artists who were among the forerunners of today's Yakuza. During times of economic depression, the con men would be sent to gamble with day laborers on public works projects. In exchange for a commission fee, the swindlers returned some of the government's money!
As many games, this game has a limited number of stock phrases that the enemies shout at you in combat. Many but not all of the enemies are Japanese, and those enemies who do speak Japanese often scream "Kusu gaijin!" Both these words have the accent falling on the first syllable, and the phrase means "Filthy foreigner!" Similarly, in the original language-version of Metal Gear Solid 3: Snake Eater, Revolver Ocelot insults Naked Snake with the words "... Kusu Amerikajin inu!" or "Filthy American dog!"
On 21st May 2007, the game's soundtrack by Tom Salta was made available on iTunes. On 29th May 2007, it was also released to retail on CD by Persist Records / Sumthing Distribution.