The Sumitomo Group is the preeminent Kansai keiretsu. The original zaibatsu got its start in copper mining and metal mining is still crucial field for it. The core of the Sumitomo Group includes Sumitomo Metal Mining as well as the Sumitomo Bank. Sumitomo Chemical is also part of the core. The number of companies in the group is small, twenty, compared with the forty plus in some other members of the Big Six. Most of the twenty have "Sumitomo" in their name.

The Sumitomo Group is noted for its aggressive striving for profit and growth. It is now second in terms of sales and its bank is first in terms of profits.

The Other Keiretsu