The Japanese billionaire behind a deal that will create the world's third-biggest mobile company spent his childhood in a slum, where he proudly rode in a stinking wheelbarrow filled with pig feed, pushed by his grandmother, a Korean immigrant.

The unlikely success story of Softbank Corp. President Masayoshi Son has taken another leap with his latest mega-deal, announced Monday, to take a 70 percent stake in U.S. mobile carrier Sprint Nextel Corp. for $ 20 billion.

The biggest foreign acquisition in the history of Japan Inc. underlines Son's unusual status in a corporate culture that has frowned upon risk taking. But his high-profile acknowledgement of his Korean roots may be what most sets Son apart in Japan.

Son is Japan's second richest man with a $ 7.2 billion fortune, according to Forbes.