Since then, however, the benchmark stock index has struggled to find upward momentum,weighed by a slightly stronger yen. As of last Friday, the Nikkei was down 2.9 percent on the December 8 high at 17,511. The yen has also wobbled against the dollar: after weakening by nearly 15 percent between mid-October and early December, it strengthened to the 116 level in mid-January before weakening back down to 118 at the end of last week.

But bumper growth in corporate profits on the back of a weaker yen will send the Nikkei back on an upward trend, according to stock strategists. Quarterly earnings are forecast to rise by 15 percent for the 312 companies that are included in the Russell Nomura index, according to Motomura. The index includes the biggest companies listed on the Tokyo Exchange, excluding the financials.

Read MoreA busy week ahead for Japan, Asia’s central banks

Japan’s third quarter earnings season will go into full swing from the first week of February.

The positive momentum is back– “not only does the ECB’s QE program put worries about the euro zone behind us, but oil prices appear to have bottomed out,” said Daiwa Securities’ senior Japan equities strategist Takuya Takahashi. He sees the Nikkei rising above 18,000 in the latter half of February, after the earnings reports are out.

Groping for catalysts

Some beg to differ with those bullish views, however.

“They are groping for catalysts,” said Credit Suisse Japan economist Takashi Shiono. If anything, the kind of rally the strategists are forecasting would be a sign of an asset bubble propped up bythe illusion that quantitative easing is working, he said.

Central banks can’t win the fight against falling oil prices, he said. He sees cheap oil tipping core consumer inflation in Japan into negative territory, to -0.3 percent in April and to -0.5 percent in May. The BOJ itself cut last week its annual inflation forecast to 1 percent for the fiscal year starting this April.

Another worrying sign is the fall in long-term government bond yields, which is evidence the broader financial markets, beyond stock investors, don’t believe economic growth is anywhere on the horizon. Earlier last week, the yield on 30-year bonds fell to a record low of 1.067 percent, while shorter maturities also touched record lows, with the five-year dipping into negative territory before bopping back into the positive, albeit of just 0.017 percent.

Still, central bank easing does tend to lift stock prices, conceded Shiono. He expects that another round of easing by the Bank of Japan in April or May could lift the Nikkei to 18,500.