Japan's three leading automakers expect a stronger yen will cost them around $14 billion in lost operating profit this year alone — just as they need to invest more in everything from cleaner fuel to driverless cars.

After three years of supernormal profits on the back of a weaker currency, Toyota Motor, Nissan Motor and Honda Motor now face a reality check after the yen has turned around.

While the recent years' currency boon filled automakers' coffers — Toyota alone has around $10 billion in cash — a squeeze on margins will put them under pressure to focus their investments, analysts say.