Six and a half years after unleashing massive monetary easing, the Bank of Japan failed to raise inflation as planned. Now clouds hang over the Japanese economy — as they do others worldwide — because of the U.S.-China trade war, slowing global growth and rising economic uncertainty.

Other central banks will likely release fresh rounds of monetary easing, but the BOJ is out of ammunition. It bought up almost every asset it could by driving interest rates down. Having shot its "bazooka," what can the BOJ do next to tackle a future recession?

Hiroshi Ugai, chief economist at JPMorgan Securities Japan Co. and a former BOJ staff member, believes the central bank must enter a new agreement with the government. The previous agreement, issued as a joint statement in January 2013, called for cooperation to expand the economy.