Tokyo stocks were mixed on Monday morning, with the Nikkei 225 giving up early gains as profit-taking kicked in after the benchmark index hit its highest level since the 2011 quake-tsunami disaster.
The Nikkei was down 0.20 percent, or 21.91 points, at 10,666.20 by the break as the yen gained in forex trade, while the Topix index of all first-section shares was flat, inching up 0.01 percent, or 0.12 points, at 888.63.
Tokyo stocks jumped 2.82 percent on Friday, the first trading day of 2013, as the yen tumbled on relief over a US deal to avert the "fiscal cliff" of tax hikes and huge spending cuts.
The Nikkei ended 2012 at its highest level since the twin disasters, which set off the crisis at Fukushima, the worst nuclear accident in a generation.
"The market sports all the technical signs of being overheated, but the momentum of the falling yen continues to attract investors," SMBC Nikko Securities general manager of equities Hiroichi Nishi told Dow Jones Newswires.
"There are plenty of sellers in the market, but they are overwhelmed by players who are finding that they can't afford to not buy."
In currency trading, the greenback bought 88.02 yen in Tokyo morning trade, slightly down from 88.15 yen in New York on Friday, after earlier hitting a peak of 88.41 yen, its highest level since mid-July 2010.
The euro was also weaker against the Japanese currency at 114.92 yen from 115.19 yen, while it slipped to $1.3057 from $1.3067.
US economic data Friday showed a modest 155,000 jobs were added in December, not enough to spark great optimism but showing strength given the unsteady political policy climate of recent months.
In addition the latest ISM index on the service sector showed unexpected growth in December, the fastest in 10 months, led by new orders and employment.
That helped the Dow Jones Industrial Average finish up 0.33 percent at 13,435.21 on Friday.