The benchmark Nikkei index at the Tokyo Stock Exchange rose 28.02 points to 9,648.84 by the lunch break.
The Nikkei may trade in a range of 9,600-9,750, supported by the weak yen and Wall Street's rally, Kazuhiro Takahashi, general manager of investment strategy at Daiwa Securities, told Dow Jones Newswires.
The dollar rose to 81.67 yen in Tokyo midday trade from 81.60 yen in New York late Thursday.
The outcome of a Bank of Japan two day policy board meeting will be of note Friday, Takahashi added.
The central bank is widely expected to keep ultra low interest rates unchanged without adopting additional easing measures, one day after data showing Japan had slid back into recession after the March 11 disasters.
The utilities sector faced a heavy sell-off again, battered by a possible breakup of energy companies and difficulty in containing the nuclear crisis, said Hideyuki Ishiguro, a strategist at Okasan Securities.
He pegged the Nikkei's range for Friday at 9,550-9,680, noting that any fresh comments on the sector from government officials will be closely watched.
Tokyo Electric Power, which operates the crippled Fukushima Daiichi nuclear power plant, was down 0.83 percent at 355 yen before its release later Friday of earnings results for the year to March.
The utility is widely expected to report a net loss of more than one trillion yen ($12 billion).
Chubu Electric Power lost 3.19 percent to 1,241.
Takeda Pharmaceutical, which after Thursday's close announced a 9.6 billion euro ($13.6 billion) deal to buy Swiss drugmaker Nycomed, firmed 0.26 percent to 3,800 yen.
US stocks overcame disappointing economic data Thursday and ended the day in positive territory, while a dazzling market launch by career-focused social-networking firm LinkedIn revived dreams of another dot-com boom.
The Dow Jones Industrial Average rose 44.99 points (0.36 percent) to 12,605.17 and the broader S&P 500 edged up 2.88 points (0.21 percent) to 1,343.56.