Tokyo's Nikkei slipped 0.36 percent, or 34.87 points, to 9,556.65 as dealers nervously awaited the start of the earnings season, which will provide the first glimpse of the economic impact of last month's devastating quake-tsunami.
Sentiment was also weighed after Tokyo Electric Power, which operates the Fukushima nuclear plant that was crippled by the March 11 twin disasters, said it hoped to achieve a "cold shutdown" within six to nine months.
"While laying out a timeline (for the reactor site shutdown) is a positive, the timeframe could also be viewed as too long," Kenichi Hirano, operating officer at Tachibana Securities, said.
Sydney added 0.20 percent, or 9.8 points, to 4,861.9 and Hong Kong gained 0.19 percent in the afternoon.
Seoul fell 0.21 percent, or 2.78 points, to 2,137.72.
Shanghai slipped 0.37 percent in the afternoon, but traders said there was little impact from another round of monetary tightening by China on Sunday.
The People's Bank of China said it would raise the amount of money banks must keep in reserve for the fourth time this year -- its latest move aimed at cooling lending and taming prices.
The move came after data Friday showed inflation at 5.4 percent year on year in March, a 32-month high despite four interest rate hikes since October.
"The (Chinese) market wouldn't be very sensitive to the hike in banks' reserve requirement ratio as investors had anticipated the central bank would launch further tightening steps in the short run after Friday's data release," said Shanghai Securities analyst Qian Weihai.
US stocks gained on Friday as investors welcomed a 0.5 percent rise in consumer prices in March, in line with expectations.
However, core inflation -- which strips out volatile oil and food prices, and which is more closely watched by the Federal Reserve -- rose a less-than-expected 0.1 percent.
The news led the Fed to say it would bring an end to its easy monetary policy in June, dashing hopes of an early exit that would limit the amount of cash in the markets.
On currency markets the dollar was lower at 82.90 yen, compared with 83.09 in New York late Friday.
The euro also slipped after the Wall Street Journal reported the International Monetary Fund believes Greece's debt is unsustainable and has told European officials Athens should consider restructuring.
The euro's problems were compounded by Moody's cutting its credit rating on Ireland by two notches to just above junk status, citing an "expected decline" in government finances.
The euro fetched $1.4374 in Tokyo morning trading, down from $1.4431 in New York late Friday. The single European currency was at 119.17 yen, down from 119.91.
Daisaku Ueno, chief analyst at Gaitame.Com Research Institute, told Dow Jones Newswires: "Recent sharp gains in the euro so far this year may have priced in multiple rate hikes by the ECB, and resurfacing European sovereign debt issues may have offered investors a good cue to take profits."
Oil prices edged down after last week's gains, although the weaker dollar provided some support.
New York's main contract, light sweet crude for delivery in May, fell 78 cents to $108.88 a barrel in the afternoon, while Brent North Sea crude for June eased 49 cents to $122.96.
Gold opened at $1,486.00-$1,487.00 an ounce in Hong Kong, up from Friday's close of $1,473.00-$1,474.00.
In other markets:
Taipei ended flat, edging down 3.64 points to 8,714.48.
Taiwan Semiconductor Manufacturing Co was 0.29 percent lower at Tw$69.0 while MediaTek lost 4.76 percent to Tw$320.0.
Manila gained 0.41 percent, or 17.55 points, to 4,269.19.
Alliance Global Group rose 0.2 percent to 11.36 pesos, Philex Mining added 4.6 percent to 16.48 and Metropolitan Bank & Trust was 0.7 percent higher at 68.80. Cebu Air lost 3.0 percent to 76.90.
Wellington rose 0.36 percent, or 12.48 points, to 3,465.17.
Telecom was up 4.3 percent at NZ$2.06 and Fletcher Building slipped 0.4 percent to NZ$9.14.