TOKYO/SEOUL, March 14 (Reuters) - Japan and South Korea expressed concern on Saturday about the rapid declines in their currencies, saying they were ‌ready to act against excessive foreign-exchange volatility. Finance Ministers Satsuki Katayama of ‌Japan and Koo Yun-cheol of South Korea "expressed serious concern over the recent sharp depreciation of the ​Korean won and the Japanese yen," they said in a statement after their annual meeting in Tokyo. The yen and won have slid as mounting tensions from t ...