1) Yasuo Hamanaka of Sumitomo Corporation manipulated the copper market through large derivative trades, accumulating massive hidden losses over several years.
2) In 1995, changing market conditions caused copper prices to drop, exposing Sumitomo's huge long positions and resulting in over $1.8 billion in losses for the company.
3) The scandal revealed lax management and a lack of independent oversight at Sumitomo that allowed Hamanaka to dominate copper trading without detection of his risky derivative strategies. It showed the need for stricter regulation of derivatives and corporate transparency.