Did you trade primarily futures or options? Professionally or retail? How did you deal with swapping your monthly p&l into your base currency? If I remember correctly back then, the won was not freely convertible and my desk buddy who traded kospi options had to enter into NDFs to settle his pnl.
Only futures, but options played a big role. I was trading via IB and had to swap USD to Won and back when I needed to withdraw. Was really simple. It was retail for my own account.
You can't "trade" the Won with IB. You can only close out open positions in the Won created by PnL from positions denominated in Won.