Tokyo stocks slipped 0.11 percent Monday morning, weighed by losses on Wall Street last week and escalating tensions in Ukraine.
The benchmark Nikkei 225 index fell 15.62 points to 13,944.43 by the break, while the Topix index of all first-section shares added 0.47 percent, or 5.32 points, to 1,139.41.
Disappointment over the Bank of Japan's decision not to expand its stimulus drive -- and a consequent rise in the yen -- helped drag the Nikkei to a six-month low on Friday, with the headline index down 7.33 percent over the week.
That was the Nikkei's worst weekly performance since a 10 percent decline in the period after Japan's 2011 quake-tsunami disaster.
On Monday, the Nikkei was dragged lower by shares in market heavyweight Fast Retailing, operator of the Uniqlo clothing chain, falling 3.48 percent to 32,640 yen.
The retailer plunged 7.87 percent Friday after cutting its full-year earnings forecast, blaming weaker demand at home.
Last week, the tech-rich Nasdaq Composite Index led Wall Street sharply lower again, closing out a dreary week at its lowest level in more than two months.
The Nasdaq sank 1.34 percent to 3,999.73, its lowest close since February 3, while the Dow Jones Industrial Average tumbled 0.89 percent to 16,026.75.
Markets are also jittery after Ukraine's acting president accused Russia of waging war in his country's eastern belt as fresh clashes left at least two dead.
Acting President Oleksandr Turchynov declared the launch of a "full-scale anti-terrorist operation" while the United Nations Security Council announced emergency talks late on Sunday.
In forex trading, the dollar slipped to 101.54 yen, down from 101.65 yen in New York Friday afternoon.
A stronger yen is bad for shares of Japanese exporters as it dents their profitability.