Mitsubishi was founded in 1870 by Yataro Iwasaki as a shipping industry. After the Meiji-era (1868) many industries were denationalized, giving Iwasaki-san several opportunities to develop his company/zaibatsu*. At the turn of the century (1900) Mitsubishi owned more than 50 % of of the Japanese merchant fleet, various coalmines, shipyards, paper-, glass-, and steel factories. In 1874 Mitsubishi opened a new head office in Tokyo. In that year the name of the company was changed into Mitsubishi Jokisen Kaisha, alias Mitsubishi Steamboat Company, as Mitsubishi was given the management of the national postal steamboat company. By assisting the Japanese government in revitalizing several former national industries Mitsubishi gained certain privileges. In 1893 Mitsubishi Corporation was founded, becoming the main financier of the zaibatsu (after WWII called keiretsu*).
In 1919 the Mitsubishi Bank was founded and during the following decennia many companies/industries were incorporated. Among them was Nikon Corporation. Through the years the Mitsubishi keiretsu has been grown into one of the largest industrial enterprises in the world.
Below a short list of companies and industries that are member of the Mitsubishi keiretsu. Updated info can be found at https://www.misubishi.com/e/index.html
The CEO's of these companies - called the 'Friday Club' (Mitsubishi Kinyokai) - are meeting every second friday of every month for exchanging the latest (business) news. It is clear that this frequent exchange of information is strengthening mutual confidence.
Asahi Glass Co., Ltd.
Bank of Tokyo-Mitsubishi Ltd. (member of Mitsubishi Tokyo Financial Group)
Kirin Brewery Co. Ltd (producer of beer, wine, spirits and lemonade)
Meiji Life Insurance Co. (insurance/assurance company)
Mitsubishi Aluminum Co. Ltd.
Mitsubishi Cable Industries Ltd.
Mitsubishi Chemical Industries Ltd.
Mitsubishi Corporation Ltd (trading company)
Mitsubishi Electric Corporation (producer of domestic appliances like refrigerators, TV-sets, etc.)
Mitsubishi Estate Co. Ltd (real estates)
Mitsubishi Fuso Truck & Bus Co. Ltd.
Mitsubishi Gas Chemical Co. Ltd.
Mitsubishi Heavy Industries Ltd (steel)
Mitsubishi Kakoki Kaiska Ltd. (power plants, chemicals, medicines etc.)
Mitsubishi Logistics Corporation (transport & logistics)
Mitsubishi Materials Corporation (minerals & raw materials)
Mitsubishi Motors Corporation (cars & trucks)
Mitsubishi Paper Mills Ltd.
Mitsubishi Plastics Inc.
Mitsubishi Rayon Co. Ltd.
Mitsubishi Research Institute Inc.
Mitsubishi Shindoh Co. Ltd. (semi-finished products of copper and non-ferro materials)
Mitsubishi Steel Manufacturing Co. Ltd.
Mitsubishi Trust & Banking Corporation
Nippon Oil Corporation
Nippon Yusen K.K. (NYK-Line, shipping company)
Mitsubishi Construction Co. Ltd. (building and construction company)
Tokyo Marine and Fire Insurance Co. Ltd.
and - finally - Nikon Corporation
* Zaibatsu - Keiretsu (zaibatsu = money clique; keiretsu = relations/connections)
A Zaibatsu is a financial and industrial conglomerate of family-run companies. After the Meiji-era most zaibatsu's were becoming powerful groups, receiving privileges (tax exemptions, etc) by the Japanese government. Not only in Japan these zaibatsu's gave national economy a boost; also Taiwan and Korea were benefited by these 'constructions'. Via excellent connections with Japanese politicians the zaibatsu's were controlling - in the 1930's - more than 1/3 of all bank-balances, 1/3 of foreign trade and more than 50 % of shipbuilding, shipping and heavy industry. During those years the army tried - vainly - to break that monopoly. The American occupation (1945-1951) abolished these zaibatsu's formally, but in fact they were replaced by the keiretsu's.
A Keiretsu - nowadays - is a conglomerate of companies and industries linked together via mutual interests, assistance and sharing capital (joint shares, etc.). Not only to assist and control each other but also to avoid 'internal' competition and hostile takeovers. During the 1990's many keiretsu's were seriously hit because of secret deals with and donations to politicians and political parties in Japan. Japan's economical and political life lost its face. In 1995 the Bank of Tokyo had to lower the interest rate to a historic o.5 %. Unemployment reached a historic top at 4.4 %. In 1999 Japan Leasing Corporation was declared bankrupt, and the Long-Term Credit Bank was saved by the bell by nationalization. Nikon Corporation has problems in surviving.
Large keiretsu's are Mitsui (incl. Fujifilm, Sony and Toshiba), Mizuho (incl. Canon, Ricoh), MUFG (incl. KonicaMinolta, Hoya), Yasuda, Sumimoto, Okura and Suzuki.