Buying 1 billion won in cash gift certificates while dressed shabbily looks suspicious

Making 1 billion won in cash is difficult.
Having a balance of 1 billion won in a bank or securities account is common, but if you even attempt to withdraw just 100 million won in cash, the bank will find it uncomfortable and report it to the FSS as a suspicious transaction.
A bank balance of 1 billion won feels quite different from having 1 billion won in cash.