Tokyo shares rose 0.77 percent on Tuesday morning in largely directionless trade with few solid cues and a weaker dollar capping the market's gains.
The benchmark Nikkei 225 index added 112.23 points to 14,770.27 by the break, reversing a 0.70 percent decline at the open, while the Topix index of all first-section shares was 0.40 percent, or 4.87 points, higher to 1,221.40 in low-volume trading.
"The yen has shown signs of pesky resilience, which will act to cap further stock market advances," said SMBC Nikko Securities general manager of equities Hiroichi Nishi.
"Otherwise the expectations that had been built into the market on the back of the Sunday upper house election results have already been vented, leaving the market short of trading cues before corporate earnings reporting season cranks up in earnest."
Major Japanese firms including Panasonic, Honda and Nintendo are set to report their quarterly results next week.
Japanese prime minister Shinzo Abe's win on Sunday in upper house elections gives him full control of both houses of parliament and the legislative muscle to press on with a growth scheme dubbed "Abenomics", which is expected to include some unpopular reforms to the economy.
Buoying sentiment, Tokyo upgraded its view of Japan's economy for the third-straight month on Tuesday, saying it was showing signs of recovery.
In stock trading, Fukushima operator Tokyo Electric Power tumbled 6.40 percent to 658 yen as workers at the crippled plan reported steam inside a battered reactor building for the second time in less than a week.
The site has suffered a litany of problems since it was swamped by Japan's quake-sparked tsunami two years ago.
Camera giant Nikon rose 1.04 percent to 2,322 yen, Sony jumped 3.56 percent to 2,298 yen, while Uniqlo clothing chain operator Fast Retailing rose 1.09 percent to 36,850 yen.
Nippon Steel & Sumitomo Metal was 3.01 percent higher to 308 yen on a report in the leading Nikkei business daily that said the firm and Toyota has agreed on a 10 percent price hike for sheet steel used to make automobiles.
In forex trading, the dollar fetched 99.49 yen in late morning Tokyo trade, down from 99.59 yen in New York.
US stocks ended flat Monday after a series of mediocre earnings reports limited buying enthusiasm.