The Nikkei benchmark added 0.4 per cent to 16,945.43 by 0206 GMT, and was on course for its first gain in five sessions. On Tuesday, the average fell 3.0 per cent, its steepest daily fall in 10 months. Since Dec. 26, the benchmark has lost 4.6 per cent.
Other major markets in Asia were mostly flat.
With few developments in Greece's unclear future within the euro zone, and falling oil prices seen as stimulatory to worldwide consumer demand, market participants saw the Nikkei's sell-off as having run its course.
"There's no change in the fundamentals. The market has discounted bad news from Greece, and the Nikkei's now at a reasonable level," said Takashi Hiroki, chief strategist at Monex, Inc. "The crude oil price decline will be a positive factor for the Japanese economy and company earnings."
The oil market rout, which began in mid-2014 on the back of a supply glut, has sent prices to their lowest since spring 2009 and has caused investors to scurry for safe-havens such as the yen and government bonds.
That pushed the Japanese currency up against the dollar to as high as 118.35, causing investors to sell exporters' shares, before the yen weakened again to 119.05 by 0215 GMT. The yen reached a 7-1/2-year low of 121.84 against the dollar on Dec. 8.
After initial losses, exporters strengthened, with Toyota Motor Corp adding 2.1 per cent and Honda Motor Co Ltd gaining 0.2 per cent.
Large-cap Softbank Corp gained 1.6 per cent, while Uniqlo clothes brand owner Fast Retailing Co Ltd added 0.2 per cent.
Meanwhile, buying by the Bank of Japan and the government public pension fund, the world's largest, is supporting sentiment, said Masayuki Doshida, senior market analyst at Rakuten Securities Inc.
The central bank bought 71.5 billion yen ($602.3 million) worth of ETFs on Monday and Tuesday.
The BOJ's aggressive asset purchasing programme, centered on investment in exchange-traded funds, has been a key driver of the Nikkei's 7.6 per cent rally since Oct. 31, when the BOJ shocked markets by announcing additional monetary easing.
The broader Topix was flat at 1,361.07, while the JPX-Nikkei Index 400 dropped 0.1 per cent to 12,322.98.
Copyright: Thomson Reuters 2015