Softbank Corp. has expanded at breakneck speed since its origins as a software distributor three decades ago manned by CEO Masayoshi Son and two employees. (The two left after Mr. Son told them the company would someday report annual sales of ¥50 billion, fearing for the state of his mind. The company Thursday reported a quarterly net profit triple that and said it expects sales of at least ¥6 trillion in the year to March).

Mr. Son says his corporate group now includes stakes in more than 1,300 companies. But who are they?

...