Tokyo stocks opened 0.51 percent lower on Wednesday, tracking a fall on Wall Street as the second-quarter earnings season kicked off.
The Nikkei 225 index fell 78.00 points to 15,236.41 in the first 20 minutes of trade.
"The market remains in an overheated state, and more selling down the 15,000 mark would not be out of the question after six weeks of mostly steady buying and nearly 10 percent in gains," said Nikko Securities general manager of equities Hiroichi Nishi.
The dollar was also weaker, quoted at 101.50 yen, against 101.57 yen in New York Tuesday. A weak yen is bad for exporters and financials.
In the US market, the Dow Jones Industrial Average dropped 0.69 percent to close at 16,906.62 Tuesday, while the tech-rich Nasdaq Composite Index slumped 1.35 percent to 4,391.46.
Earnings season for the second quarter kicked off in the United States after the markets closed, with the release of financial results from aluminium producer Alcoa.
In Japan, many blue-chip companies are due to announce results of their April-June quarter from later this month.
-- Dow Jones Newswires contributed to this story --