The Yakuza (pronounced with the accent on the first syllable) are organized crime syndicates much like the American mafia. They are very organized and follow a very strict code of conduct with approximately 100,000 members in dozens of organizations. Their violent deeds are broadcasted on TV, radio, and newspaper, and they are feared and hated by the general public.
After Kenji's family is killed in the 2011 tsunami in Kenji's Power, he goes to live with his uncle, who, to his horror, turns out to be a Yakuza. Many Yakuzas tattoo most of their bodies by a painful process whereas the ink is inserted beneath the skin using non-electrical needles. Because tattoos are associated with the Yakuza, people with them are not allowed in hot spring pools, fitness centers, and other places where tattoos are visible. Kenji's uncle, like most Yakuzas, keep their tattoos hidden beneath long-sleeved, collared-shirts.
To counter their notorious connection to drug and human trafficking, racketeering, loan sharking, and other crimes, many Yakuza organizations help when natural disaster hits. After the massive earthquake and tsunami in 2011, they supplied food, water, blankets, and sanitary products to the victims. Even though they help in charitable ways, never get involved with them!