Japanese stocks tumbled Thursday, leading losses across Asian stock markets, after the Bank of Japan kept its monetary-easing policies unchanged. 
Japan’s Nikkei Stock Average NIK, -3.05% ended down 3.1%. Thursday’s losses were enough to edge the Nikkei past China’s main stock index as the worst-performing benchmark in Asia so far this year. 
As of Thursday’s close, the Nikkei is down 18.9% in the year to date, compared with the Shanghai Composite Index’s 18.8% decline. 
After the BOJ decision, stocks in Japan fell sharply as the yen tested its strongest levels against the U.S. dollar in nearly two years. Shares of insurers and auto makers sank. Dai-ichi Life Insurance Co. Ltd. 8750, -3.54% fell 3.5%, and Nissan Motor Co. 7201, -4.33% was down 4.3%.