Shares of Mitsubishi UFJ and Mizuho Financial Group fell by the most on record on Monday, as the stock market plunge sent Japanese bank stocks tumbling together. Shares of Japan's largest banks, MUFG, fell 18%, Mizuho Bank fell 20%, and Sumitomo Mitsui Financial Group fell nearly 16%, also a record high, by the end of the day. The three companies have lost about 12 trillion yen ($85 billion) in market value over the past two trading days. The plunge in Japanese bank stocks highlights how sensitive they are to fluctuations in the outlook for interest rates. The sharp falls in bank stocks highlight the challenges facing the Bank of Japan in trying to "normalize" monetary policy.