TOKYO (Bloomberg) -- Japan Inc. is already counting the cost of Brexit. The yen's extended surge after UK's decision to exit the EU has turned the outlook for a gain in annual profit to the first decline in four years.

Take Toyota Motor Corp. Since the June 23 Brexit vote, the mean forecast for net income at the world's biggest automaker has slid to $16.5 billion, with four analysts cutting their predictions by an average $2.3 billion for the fiscal year that started April 1. The referendum outcome triggered the yen's biggest one-day advance in almost 18 years, taking its gains against the dollar in 2016 to 17 percent, the best among developed nations.

Profit estimates for Nissan Motor Co. and Canon Inc. were also cut by analysts after the referendum vote pushed up the yen, paring the value of income from overseas. Growth concerns in Europe after the referendum and the currency's gains are casting a shadow on exports and threatening to derail Prime Minister Shinzo Abe's efforts to free Asia's second-biggest economy from deflation.

"Abenomics is finished," said Takuji Okubo, Tokyo-based chief economist at Japan Macro Advisors. "The yen appreciation will be the largest impact from Brexit to Japan. Japanese corporate profits will decline and how much they will decline depends on how much the yen appreciates. There is significant risk the yen could increase very sharply to 90 yen against the dollar."

Earnings at 200 of Japan's largest companies would drop about 3.6 percent in the fiscal year, Daiwa Securities Group Inc. estimates, based on the yen averaging 100 against the dollar and 115 against the euro during the year.

"The yen is strengthening against several currencies and this is weighing heavily on earnings at Japanese automakers," Tokyo-based analysts led by Kota Yuzawa at Goldman Sachs Group, wrote in a report. "We revise Goldman Sachs estimates following the UK's referendum vote to leave the EU."

The company lowered its Toyota operating profit forecast by 21 percent to 1.78 trillion yen ($17.4 billion) for this fiscal year.

Cost-cut efforts

Toyota said its approach to maintaining production of 3 million vehicles in Japan hasn't changed, and that its system isn't dictated by "short-term factors such as exchange rates, regardless of how much the business environment fluctuates." If analysts are right with their predictions, it would be Toyota's first drop in profit in five years.

Nissan said it desires exchange-rate stability and it is "always working to create a business structure that minimizes exchange-rate volatility."

Suzuki Motor Corp. said the Indian rupee and the euro have the biggest impact on its earnings. "We are going to cope with a stronger yen through further cost-cut efforts and local production," Takashi Iwatsuki, a corporate director in charge of overseas sales at Suzuki, told shareholders at a meeting last week.

Pretty serious

"You're in trouble if you're exporting," said Edwin Merner, president of Atlantis Investment Research Corp. in Tokyo. "If the currency changes slowly over a period of a couple of years you can adjust, but if it moves very quickly like it has, you cannot adjust so quickly -- it's pretty serious."

The Brexit vote may cost automakers worldwide about 2.8 million light-vehicle sales through 2018, researcher IHS Automotive said in its latest projections for the industry.