Tokyo stocks closed 1.19 percent lower on Thursday, hit by profit-taking after the index enjoyed its biggest one-day percentage gain this year.
The Nikkei 225 lost 121.07 points to 10,039.33 after surging 2.39 percent Wednesday to close above 10,000 for the first time since the start of April.
The Topix index of all first-section issues was down 0.09 percent, or 0.73 points, at 838.61.
"The selling is thus far light compared with Wednesday's surge," Okasan Securities strategist Hideyuki Ishiguro told Dow Jones Newswires.
A director of equity trading at a foreign brokerage also said: "Foreign investors continue to buy into the market, but we're seeing more passive fund interest now, as opposed to the heavy hedge fund interest of the last few weeks."
Stocks had risen on the back of a weaker yen following a landslide win by the opposition Liberal Democratic Party and its ally in Japan's national elections on Sunday.
The Bank of Japan on Thursday decided to expand an asset-buying programme -- its main monetary policy tool -- by 10 trillion yen ($119 billion) to 101 trillion yen as part of efforts to spur the world's third-largest economy.
The central bank kept interest rates unchanged at between zero and 0.1 percent, and said it would look at reviewing its target inflation rate.
"Overall, the BoJ move was within market expectations, and contained little that would directly affect the tech-stock dominated Nikkei," said Norihiro Fujito, senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities.
The BoJ was under scrutiny to see if its stance or rhetoric reflects an increase in pressure from the incoming coalition to further loosen monetary policy.
The yen was at 83.98 yen in Tokyo afternoon trade, compared with 84.39 yen in New York Wednesday afternoon. The euro bought 111.04 yen and $1.3219 against 111.59 yen and $1.3226.
Mitsubishi Motors was down 5.49 percent at 86 yen after it widened a recall over an oil leak issue on vehicles sold in Japan to about 1.7 million units, prompting a rebuke by the transport ministry.
Mitsubishi Electric was up 2.28 percent at 761 yen, discounting a report in the Nikkei economic daily that the firm will pay 50 billion yen to Japan's defence ministry for overcharging for defence equipment.
Clothing giant Fast Retailing tumbled 4.05 percent to 20,370 yen on profit-taking following a recent surge, while Softbank lost 3.75 percent to 2,998 yen and Canon fell 2.89 percent to 3,355 yen.