Tokyo stocks opened 0.50 percent higher on Wednesday with the lower yen heartening investors.
The Nikkei 225 index at the Tokyo Stock Exchange was up 50.85 points at 10,130.97 in the first 20 minutes of trading as the Japanese currency dipped to a new 20-month low past 85.00 yen against the dollar.
The benchmark index was likely to trade in a narrow range with a slight upward bias, according to traders, as US markets were on Christmas holiday Tuesday, and few other incentives were seen stirring the markets.
"Steady downward pressure on the yen is supporting stocks, and this should lead to an early rise for the major indexes," followed by some selling in the afternoon, said SMBC Nikko Securities general manager of equities Hiroichi Nishi.
The dollar rose past 85.00 yen in early Asian trade on Wednesday on expectations that the Bank of Japan would take more monetary easing steps under political pressure from the incoming government.
The dollar was at 85.10 yen shortly after 0000 GMT, the first time above 85.00 yen since April 2011 and up from 84.78 yen in Tokyo afternoon trade on Tuesday.
A high yen is a negative for Japanese markets as it erodes exporters' revenue.
The Japanese currency has been declining as incoming prime minister Shinzo Abe, whose Liberal Democratic Party won a landslide national election last week, steps up pressure on the central bank to take bold easing steps.
Abe is to be named prime minister later Wednesday, after he swept to power on a hawkish platform of getting tough on diplomacy while fixing the economy with active fiscal spending and monetary easing.