Japan's earnings season has drawn to a close with the sharply weaker yen helping inflate profits at some of the nation's top exporters, but, some commentators warn, the drop is not all good news. Sony booked its first annual profit in five years, Toyota more than tripled its earnings in the fiscal year to March and the head of rival automaker Nissan hailed the taming of the currency. "I have been talking about the unbelievable strength of the yen for many years," Carlos Ghosn said after the firm released its earnings this month. "I'm very happy to see that finally we are getting in neutral territory by having the yen at 100 yen to the dollar." In late 2011, the dollar hit a low around 75 yen, partially as a result of its safe-haven status when the euro area crisis and global uncertainty sent investors piling into the currency. Japanese firms wailed, bemoaning the rocketing cost of their products overseas and the shrinking value of their repatriated profits. Many scrambled to cut costs and shifted ever more production away from high-cost Japan. But things changed with the election last December of tough-talking Prime Minister Shinzo Abe, who promised a flood of government spending as he harangued the central bank, then replaced its head with a man who unleashed massive monetary easing. The yen has since dropped like a stone. On Friday the dollar was buying around 102.50 yen. The plunge has sparked criticism, particularly in Europe, that Tokyo engineered the unit's decline to gain a trade advantage. Critics said it risks sparking a global battle among rival nations intent on driving down their currencies. Abe denies the claim, saying it is just the result of renewed efforts to boost slow growth in the world's third-largest economy with policies that also happen to push down a currency's value. Ghosn applauded the Japanese premier's policy moves, dubbed "Abenomics", saying Nissan had been "begging" for a cheaper yen for years. "Companies are starting to build up more production, people are starting to invest again, the stock market is up, foreign companies are more interested in Japan," the auto executive said. The Tokyo stock market has been surging as foreign investors pile into Japanese stocks in anticipation of brighter times ahead, pushing the benchmark Nikkei 225 index up about 50 percent since late December. And companies have been obliging with many lifting their profit forecasts for the current fiscal year through March. "The weaker yen certainly has a positive impact on Japanese companies, although it may not be enough for the Japanese economy to take off," said Nomura Securities strategist Hisao Matsuura. "And for individuals, rising import prices -- including petrol and imported food -- are harmful." That could dig into overall consumer spending at a time when Tokyo and the business sector want just the opposite, while the weak yen is sending some companies' input costs soaring, including technology giant Toshiba, whose quarterly net profit fell 62 percent. The company said this month that yen depreciation hurt its flat-panel television and personal computer businesses because it imports many dollar-denominated parts to make those goods, boosting production costs. But overall, says Masamichi Adachi, senior economist at JPMorgan, the falling yen is good news for Japan after years of struggle. "Even if there is some negative effect (from a weak yen), that would be offset by the positive effects from revitalising Japanese exporters," he said. "In terms of its impact on the Japanese economy, it's definitely a positive."