Tokyo stocks were up 1.61 percent by the break Monday after Japan's conservative opposition swept to victory in national polls, with promises from its leader to press for more central bank easing.
The benchmark Nikkei 225 index added 156.43 points to 9,893.99, while the broader Topix index of all first-section shares rose 1.19 percent, or 9.55 points, to 810.59.
Investors cheered the return to power of the business-friendly Liberal Democratic Party as the yen plunged on speculation of more central bank easing, boosting exporters' shares in the wake of Sunday's thumping LDP win.
The result also sent utility shares soaring with Fukushima operator TEPCO skyrocketing nearly 33 percent as the win signalled that any short-term plans to ditch atomic power will likely be shelved.
The LDP is viewed as more pro-nuclear than the ousted Democratic Party of Japan, which had pledged to work towards a nuclear-free country in the wake of last year's atomic crisis.
The yen briefly dived to a 20-month low against the dollar and a more than eight-month low on the euro.
Hawkish LDP head Shinzo Abe had pledged to put Japan's moribund economy back on track after years of deflation, made worse by a soaring currency that has squeezed exporters.
Topping his agenda was a promise to pressure the Bank of Japan (BoJ), which holds a policy meeting this week, into more aggressive easing policies aimed at kickstarting growth as the world's third-largest economy slips into recession.
"It's a relief rally; the vote count was pretty much as expected," said Naoki Fujiwara, fund manager at Shinkin Asset Management.
"The weaker yen is more of a factor, based on expectations of a more compliant BoJ for policy easing," he told Dow Jones Newswires.
In Tokyo trade, Nissan Motor was up 2.16 percent to 802 yen by the break and Sony rose 2.09 percent to 925 yen.
Tokyo Electric Power (TEPCO) rocketed 32.89 percent to 202 yen, Chubu Electric Power jumped 7.56 percent to 1,166 yen and Kansai Electric was up 13.68 percent at 889 yen.
Financials also gained with Nomura Holdings up 3.00 percent at 377 yen, and construction giant Obayashi rising 3.48 percent to 445 yen.
On currency markets, the dollar bought 83.99 yen, up from 83.52 yen in New York on Friday, while the euro was at 110.48 yen, from 109.94 yen in US trade.
In earlier forex trading, the dollar shot to 84.30 yen, its highest in over a year and a half, while the euro hit 111.10 yen, its strongest in over eight months.