Analysts said that foreigners and short-term investors may still be engaging in ex-dividend date buying as well as dip buying, but domestic investors have probably already closed their positions ahead of the end of the fiscal year in March.
"There is still room to rise as foreign buying on dips is likely to continue although trading may be directionless before the end of the fiscal year," said Hajime Nakajima, a wholesale trader at Cosmo Securities.
At the midday break, the benchmark Nikkei .N225 was down 0.4 percent, or 34.49 points, at 9,501.64. The broader Topix .TOPX was nearly flat at 857.58.
Analysts added that while the market remains sensitive to changes in companies' earnings forecasts before the end of the fiscal year, Japan stocks are still oversold, with the Nikkei trading about 6 percent below its 25-day moving average of 10,062.
"Although investors are alert on news flows related to changes in companies' full-year forecasts and dividend payouts, the fundamental mood should not be that bad thanks to foreign buying," said Yumi Nishimura, a senior market analyst at Daiwa Securities Capital Markets.
Before the market opened on Monday, foreigners were seen placing orders to buy 14.9 million shares, the ninth consecutive day of pre-market buying.
Separately, foreign investors' net buying of Japanese shares reached a record high during the week of March 14, the week after a devastating earthquake hit northeastern Japan, Ministry of Finance data showed, and traders said their buying would continue this week.
Overseas investors bought a net 891 billion yen ($11 billion) of Japanese stocks in the week of March 14-18, the highest since records began in 2005.
The Nikkei is expected to trade between 9,400-9,600 on Monday, analysts said.
"Investors are still having a difficult time trying to figure out which Nikkei levels seem 'reasonable'. The 9,500-level may continue to be the key level until there are clear signs that manufacturers will resume normal operations and nuclear power concerns are stabilized," said Yoshinori Nagano, a senior strategist at Daiwa Asset Management.
JFE Holdings Inc (5411.T) climbed 2.7 percent to 2,427 yen after the Nikkei business daily reported that its JFE Steel Corp will boost output of materials for temporary housing by about 70 percent by extending operating hours at a Kobe facility that makes lightweight steel H-beams.
Tokyo Electric Power Co (9501.T) nosedived 15 percent to 720 yen after it became clear over the weekend that Japan faces a protracted struggle to bring the company's quake-stricken nuclear plant under control.
Tokyo Gas (9531.T) gained 3.0 percent to 375 yen after the company hiked its net profit forecast for the business year to March 31 to 98 billion yen ($1.21 billion) from 71 billion yen on a jump in demand from factories in January and February and an increase in gas use by households due to a cold winter.
