The rising demand for liquidity also reflected waning incentives of financial institutions to invest their funds in money markets. Investing 10 billion yen overnight earns merely 273 yen, which is not sufficient to cover various transaction costs. When interest rates significantly decline, financial institutions prefer to hold funds with the Bank of Japan even without any interest earnings.
Once such  4  BIS Review 87/2001  movement spreads among financial institutions, funding in money markets becomes more difficult which will force the borrowers to build up the current account balance from a precautionary motive.