As the supervisor in both the front and back office, Hamanaka kept two sets of trading books, one reporting huge profits for Sumitomo in the buying and selling of copper spots, futures and options, and the hidden account that recorded the actual billion-dollar losses. The segregation of duties is really important to prevent these scandals from occurring. In fact, after 1996, many governmental agencies, including ones in Japan, established new rules that provided that the middle and back office should be totally separated from the front office