Instead, the companies in the group hold shares in each other, but they are limited to exchanging information and coordinating plans through regular meetings.

[1] Riemon perfected techniques that allowed the extraction of silver from copper ore, something Japanese technology had not previously accomplished.

[1] Soga passed control of the company to his son Tomomochi who managed its transformation into a major trading house[2] during the Edo period.

[6][7][8] The Meiji Restoration allowed Sumitomo to import and utilize Western machines and techniques in its mines.

[9] The diamond-shaped igeta mark is reminiscent of a type of frame placed over a well in premodern Japan and was the logo of Riemon Soga's Izumiya company.