The Japanese yen fell below the 100-per-dollar mark over the weekend, sending shivers down the spine of the Korean government, which was deeply concerned about its potential impact on the fragile Korean economy. A weak yen is set to boost Japan’s exports of autos, ships, steel products and other items at the expense of their Korean counterparts.

On Friday morning, the yen weakened to 101 per dollar in the Tokyo foreign exchange market, breaking the 100-per-dollar mark for the first time in four years. It certainly did not come as a surprise to top Korean economic policymakers, who had long been watching the yen’s continuous downward slide.

Indeed, the yen’s record setting was not as grave a threat to the Korean economy in itself as it looked. A greater threat was posed by the prospects that the Japanese currency’s decline, with the 100-yen barrier having been broken, would accelerate in the months ahead.

Based on its own survey of economists, Bloomberg reported the yen would be at 104 per dollar at year-end. The forecast may prove to be conservative. Some currency strategists at global financial institutions do not rule out the possibility of the yen plunging to 110 per dollar.

The yen’s fall would be less onerous to South Korea if the Korean currency remained stable. But the won has been strengthening against the dollar, except for a brief lull during the latest escalation of tension over North Korea’s warlike rhetoric against South Korea and the United States. According to a news report, the Korean won gained the most among the 30 major currencies of advanced and emerging economies when it rose 4.9 percent against the dollar during the past month.

When a new record was set in the yen’s exchange rate against the dollar, the won rallied to 1,082.17 per 100 yen, the highest since September 2008. The double whammy ― the won’s gain and the yen’s fall both against the dollar ― has already stunted growth in Korean exports.

Growth in Korean exports was anemic the past two months ― 0.2 percent in March and 0.4 percent in April. The Korean government and corporations were quick to blame the weak yen. But it is of no use for them to wring their hands and complain about Japan’s monetary policy.

The Korean government, which has long promised to consider regulating the flow of foreign capital into and out of the nation to stabilize exchange rates, will now have to take action and introduce some of the new regulatory regimes under its consideration, including a “Tobin tax” on foreign exchange transactions tailored to Korean needs.

Samsung Electronics, Hyundai Motor, POSCO and other Korean companies will also have to prepare themselves for the changes in the won’s exchange rates that are continuing at the detriment of their exports. They need to make themselves lean and mean through restructuring.