The 225-issue Nikkei average fell on Monday, extending losses as the yen strengthened against the dollar, while retailer Seven & I Holdings surged 23% as it received a takeover bid.
The Nikkei index closed 1.77% lower at 37,388.62, snapping a five-day winning run that pushed up the index 8.7% last week.
"The Nikkei was expected to fall this week after its sharp rally, but the yen's gain against the dollar during the session pushed that move faster," said Fumio Matsumoto, chief strategist at Okasan Securities.
"Today's move suggests that the market will remain volatile for a while."
The dollar declined broadly and slipped sharply against the yen in particular as investors bet on a dovish tone emerging in the U.S. Federal Reserve's July policy meeting minutes and Chair Jerome Powell's upcoming speech at Jackson Hole.
Chipmaking equipment-maker Tokyo Electron slipped 3.11% to drag the Nikkei the most. Robot-maker Fanuc fell 3.23%.
Bucking the trend, Seven & I surged 23% to a daily limit high as the company, whose subsidiary Seven-Eleven Japan operates the 7-Eleven convenience store chain in the country, said it received a preliminary takeover offer from Canada's Alimentation Couche-Tard.
Seven & I has formed a special committee to review the proposal but no decision has been made by either the committee or board of directors, it added.
Of the 225 Nikkei components, 191 stocks fell and 22 rose, with one trading flat.
The broader Topix fell 1.4% to 2,641.14, with Toyota falling 3.06%.