Tokyo stocks opened down 1.63 percent on Monday after the dollar fell against the yen as investors awaited the US central bank's policy meeting this week.
The benchmark Nikkei 225 index, which lost nearly three percent on Friday on a strong dollar and unencouraging corporate results and forecasts, gave up another 230.71 points to 13,899.27 at the start.
"The weak dollar is likely to continue to pin the market down pending significant buy catalysts," said SMBC Nikko Securities general manager of equities Hiroichi Nishi.
The dollar weakened Friday as traders awaited the Federal Reserve policy meeting from Tuesday amid speculation that the Fed may hold off from tapering its bond-purchase programme in the immediate future.
A strong yen is bad for Japanese exporters as it makes their products less competitive abroad.
The dollar was at 97.89 yen in early Asian trade against 98.20 yen in New York on Friday afternoon.
The euro bought $1.3286 and 130.09 yen against $1.3278 and 130.48 yen in US trade.
US stocks ended Friday narrowly in the black, with the Dow Jones Industrial Average rising 0.02 percent to 15,558.83.