Trader Pleads Guilty

Yasuo Hamanaka, once the star copper trader at Sumitomo Corp., pleaded guilty Monday to fraud and forgery in the cover-up of $2.6 billion in losses.

The trader who once controlled 5 percent of the world’s copper market acted with increasing desperation to hide 10 years of losses, prosecutors said.

The disclosure of Hamanaka’s losses last year roiled world copper markets, rocked the 300-year-old trading company, and raised fresh questions about supervision at Japanese corporations.