Gains in auto shares and high-tech exporters such as Kyocera Corp helped push the Nikkei average up 0.68 per cent by midday on Friday, following a rise in US stocks and a weaker yen.
Shares of Isuzu Motors Ltd climbed more than 3 per cent after the Nikkei business daily reported Toyota Motor Corp, Japan's largest auto maker, would outsource production of diesel engines to the truck maker.
Metal stocks such as Sumitomo Metal Mining Co Ltd rose after some bullish brokerage comments on the sector and exks," Kuramochi said.
"The Nikkei may have hit its high for the day, though. It's moving in a small range ahead of the central bank governor's comments and the weekend."
Bank of Japan Governor Toshihiko Fukui will hold a news conference in the afternoon once the central bank wraps up a two-day policy meeting. The bank is widely expected to keep interest rates unchanged at this meeting, but market players will be listening to Fukui for any hints on future rate hikes.
The Nikkei finished the morning up 120.44 points at 17,962.73 and the broader TOPIX index gained 0.64 per cent to 1,767.92.
Trade volume fell, with 876 million shares changing hands, compared with 949 million shares on Thursday morning. Advancing shares beat decliners by 990 to 553.
The dollar held near a 4-1/2-year high, hovering around 123.00 yen in early Asian trade.
A weaker yen is a boon to companies that make the bulk of their sales abroad because it boosts profits when earnings from overseas are brought home.
EXPORTERS, METAL STOCKS UP
Exporters rose, with Kyocera up 1 per cent at 12,600 yen and Honda Motor Co Ltd adding 1.9 per cent to 4,350 yen.
Shares of Isuzu rose 3.2 per cent to 649 yen and Toyota gained 1.5 per cent to 7,680 yen.
Sumitomo Metal rose 2.1 per cent to 2,700 yen, while Dowa Mining Co Ltd advanced 1.8 per cent to 1,259 yen.
Elsewhere, Bull-Dog Sauce Co Ltd leapt 7.3 per cent higher to 1,706 yen after US fund Steel Partners raised its offer price for the Worcestershire sauce maker by 7 per cent to 1,700 yen per share from 1,584 yen.
Among other gainers, Yahoo Japan Corp, Japan's largest Web site, jumped 4.1 per cent to 43,450 yen after the company said it had tied up with Apple Inc from Thurs.