The monetary base in Japan was down 3.4 percent on year in May, the Bank of Korea said on Tuesday - coming in at 656.0.12 trillion yen.
Banknotes in circulation was down 2.0 percent on year, while coins in circulation fell 1.4 percent.
Current account balances sank an annual 3.7 percent, including a 0.8 percent drop in reserve balances.
The adjusted monetary base was up 12.7 percent on year at 646.138 trillion yen.