The yen broke through the 156 mark overnight, as the Federal Reserve's hawkish rate hike pushes the Bank of Japan to a "high-pressure moment."

After the Federal Reserve's hawkish rate increase, the yen fell sharply, raising the stakes for the Bank of Japan's policy meeting on Friday. Strategists warned that unless officials can convince the market that further monetary tightening is coming, the yen may continue to weaken.