Japan is being treated to a juicy spectacle as two of its richest and most innovative entrepreneurs brawl in public over Internet market share and visions for the future. But what's most important about the fight between Masayoshi Son and Hiroshi Mikitani is the example it's setting.

The two men have much in common. They are self-made billionaires who founded game-changing technology companies — Son with mobile-phone carrier SoftBank Corp., Mikitani with e-commerce giant Rakuten Inc. Each is his company's largest shareholder, fully fluent in English (a rarity in corporate Japan) and U.S.-educated (Son at the University of California at Berkeley; Mikitani at Harvard University). Both are married with two kids. Both make splashy investments in overseas Internet companies (Son in Alibaba Group Holding Ltd.; Mikitani in Pinterest Inc.). Both are sports nuts who own baseball teams.

Son and Mikitani are also the faces of New Japan and unapologetic critics of Japan Inc.'s clubby, insular ways. They oppose nuclear power, a stance that puts them in direct conflict with the ruling Liberal Democratic Party and Japan's powerful business lobby, Keidanren.