This file photo shows Kenichi Watanabe (L), Nomura Holdings CEO, and Koji Nagai, Nomura Securities president, during a briefying in Tokyo, in June. The head of Japan's biggest securities firm resigned... more 

This file photo shows Kenichi Watanabe (L), Nomura Holdings CEO, and Koji Nagai, Nomura Securities president, during a briefying in Tokyo, in June. The head of Japan's biggest securities firm resigned on Thursday in the wake of an embarrassing insider trading scandal, part of a widening national probe into the widespread practice less