A rash of scandals and a government crackdown are showing how mob-linked investors--the sokaiya--prey on some of Japan's biggest companies. Can business break free?

Corporate extortionist? No way. Satoshi Yamamoto prefers to be called a shareholder activist. His small, Tokyo-based publishing company, Rondan Doyukai, invests in Japanese companies and publishes stories on corporate misdeeds in a magazine, newsletter, and even a World Wide Web site ( Insists Yamamoto: "We are professional shareholders."

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