I love me a good Steve Jobs anecdote.

Son sat down with Charlie Rose on Monday and offered background on Apple’s initially exclusive iPhone partnership with SoftBank.

According to Son, the meeting with Job]s came as he was planning to enter the mobile phone business. Before jumping in, he first wanted a weapon to wield against Japan’s undisputed No. 1 carrier NTT DoCoMo and went to Apple with an idea for a handset.

“I brought my little drawing of [an] iPod with mobile capabilities,” Son said. “I gave [Jobs] my drawing, and Steve says, ‘Masa, you don’t give me your drawing. I have my own,” Son said. “I said, ‘Well, I don’t need to give you my dirty paper, but once you have your product, give me for Japan.’ He said, ‘Well, Masa, you are crazy. We have not talked to anybody, but you came to see me as the first guy. I give to you.'”

But wait, there’s more.

Before leaving, Son proposed that Jobs put down the exclusivity agreement in writing, but at that point the iPhone project was still a secret. Jobs also reminded Son that he did not yet own a mobile phone carrier in Japan.

“I said, ‘Look, Steve, you gave me your word, I bring a carrier for Japan.’ And I did,” Son said.

SoftBank would later go on to buy out and rename Vodafone Japan’s network in late 2006.

The Japanese telecom giant now owns U.S. carrier Sprint, as well as stakes in some 1,000 companies including Yahoo! Japan and Alibaba.

Son is on a shrewd campaign to get approval for SoftBank owned Sprint to merge with T-Mobile. The Charlie Rose interview was one stop along the way.