The Japanese economy is in trouble, so are many others

10-year Japanese government bond yield falls below zero, which means investing in risk free assets will have negative returns, if we assume 10-year Japanese government bond is risk free according to its good record. This is caused by people's concerns about the Japanese economy as well as the world economy. However, this leads to other questions that how commercial bank interest rates could change. Deposits saving in banks are usually considered as risk free as well; however, when there is a bank run, it will be no longer to be risk free. Therefore, commercial bank interest rates cannot be lowered, as lowering interest rates could increase the risk of bank runs, as the public may be afraid of having negative interest rates. However, if the interest rates stay high, banks have to find  effective ways to seek profits. Under the current circumstances, profits earned from lending are cut by the decrease in investment due to worries over the health of the world economy. Therefore, banks may face another big problem after the financial crisis. In addition, storing cash at home could also be considered as almost low risk. Cash has a constant nominal returns of zero. Especially under the environment of deflation, cash becomes a better choice compared with other types of investment. This largely increases the probability of bank runs. Therefore, I think that the negative 10-year government bond yield may be signaling another financial crisis in Japan; meanwhile we can many other economies have similar conditions as Japan does, which is very worrying.