Mitsui clan (三井家 Mitsui-ke?) is one of the most powerful families of merchants and industrialists in Japan.
The Mitsui enterprise made its debut in 1673 when Mitsui Takatoshi (1622–1694), son of a sake brewer, established Echigo-ya, a dry goods department store in both Edo and Kyoto. Meeting with great success, Takatoshi extended his services to moneylending and exchange. In 1691 the Mitsuis were officially chartered as merchants of the Tokugawa shogunate which ruled during that time. Three years later the family members set up their first constitution, which included details about the amount of property due to each branch as well as the duties of the family council, a periodical assembly that controlled business and other personal matters.
In the late Edo period, the Mitsuis were the richest and most eminent family in Japan, their business being thoroughly encouraged by the government of the time. After the Meiji Restoration, the family switched allegiance to the Meiji government.
In 1909, a Mitsui controlled holding company took over the business, with Mitsui thus becoming a zaibatsu of more than 150 companies operating financial, industrial and commercial industries.
As part of the Japanese plans for the exploitation of China, during the 1930s and '40s the subsidiary tobacco industry of Mitsui zaibatsu had started production of special "Golden Bat" cigarettes using the then-popular in the Far East trademark. Their circulation was prohibited in Japan and was used only for export. Local Japanese secret service under the controversial Imperial Japanese Army General Kenji Doihara had the control of their distribution in China and Manchuria where the full production was exported. In the mouthpiece of each cigarette a small dose of opium was concealed, and by this subterfuge millions of unsuspecting consumers became drug addicted simultaneously creating huge profits. The mastermind of the plan, Doihara, was prosecuted and convicted for war crimes before the International Military Tribunal for the Far East, sentenced to death in ".. pursued a systematic policy of weakening the native inhabitants' will to resist (. . . ) by directly and indirectly encouraging the increased production and importation of opium and other narcotics and by promoting the sale and consumption of such drugs among such people."; but no actions ever took place against the company which profited from their production. According to testimony presented at the Tokyo War Crimes trials in 1948, the revenue from the narcotization policy in China, including Manchukuo, was estimated in 20 to 30 million yen per year, while another authority stated during the trial that the annual revenue was estimated by the Japanese military at US$300 million a year, a colossal amount for the time.