Tokyo stocks rose 2.10 percent Friday morning, taking a cue from Wall Street, where the Dow hit a record high for a third straight day, while the yen weakened further against the dollar.
The benchmark Nikkei 225 index, which ended at a four-and-a-half-year high on Thursday, added 251.03 points to 12,219.11 by the break. The Topix index of all first-section shares was up 1.23 percent, or 12.37 points, at 1,016.72.
Shares were given a fillip as the dollar climbed to 95.13 yen in Tokyo morning trade, from 94.83 yen in New York late Thursday.
The euro was trading at $1.3095 and 124.59 yen, against $1.3107 and 124.28 yen.
The yen weakened partly because investors anticipated more aggressive monetary policy from the Bank of Japan, which will be headed by a new governor this month, dealers said.
"Buying is primarily yen-driven, however, investors aren't clamouring for exporter shares as before," Tachibana Securities market analyst Kenichi Hirano told Dow Jones Newswires.
"Many see the market as bought up to the point that weak yen-based earnings improvements are near fully priced in; thus further rises based solely on this logic may be progressively more difficult to realise," he added.
The Dow Jones Industrial Average ended at an all-time high for a third day in a row, adding 0.23 percent to 14,329.49.
Buying sentiment was helped by data showing jobless claims had fallen a day after figures showed a rise in jobs growth in the private sector.
In Tokyo technology exporters were mostly higher, with Advantest climbing 4.10 percent to 1,394 yen.
GS Yuasa, supplier of lithium-ion batteries to Boeing's troubled 787 Dreamliner, surged 8.00 percent to 472 yen, as US safety regulators said Thursday they are still seeking what exactly caused a battery fire on a Japan Airlines Boeing 787 plane.