Tokyo stocks were 0.42 percent higher Wednesday morning as the yen tumbled on speculation that incoming Japanese premier Shinzo Abe would keep up his pressure campaign for more central bank easing.
The benchmark Nikkei 225 index added 42.70 points to 10,122.82 in morning trade, while the broader Topix index of all first-section shares climbed 0.50 percent, or 4.20 points, at 842.21.
The Nikkei was likely to trade in a narrow range with few other trading cues, with Wall Street -- often a key signal for the Tokyo market -- closed on Tuesday for the Christmas holidays.
"Steady downward pressure on the yen is supporting stocks, and this should lead to an early rise for the major indexes," said SMBC Nikko Securities general manager of equities Hiroichi Nishi.
In forex trade, the dollar soared past 85.00 yen on rising expectations that the Bank of Japan would take more monetary easing steps as it faced political pressure from the incoming government.
The greenback bought 85.10 yen in midday Tokyo trade, the first time it has climbed above 85.00 yen since April 2011 and up from 84.78 yen in Tokyo afternoon trade on Tuesday.
A strong yen is a negative for Japanese markets as it erodes exporters' revenue and makes their products less competitive overseas.
The Japanese currency has been declining as Abe, whose Liberal Democratic Party won a landslide national election this month, 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.
Last week, Japan's central bank launched its third round of easing since September, after its counterparts in the US and Europe also ushered in huge measures. The move was widely seen as a bow to Abe's pressure campaign.
-- Dow Jones Newswires contributed to this article --