This paper presents a simulation model based on the growth rate, the inflation rate, and the consumption tax rate in the future. Future tax revenues and fiscal expenditures are projected using regression models estimated from past data. The fiscal situation is called unsustainable if the outstanding amount of Japanese government bonds (JGBs) becomes higher than the level of private sector financial assets. We focus on the general account of the central government, which is the source of JGB issues. We find that the higher the economic growth, the more likely it is that the fiscal situation is sustainable. When a larger portion of interest income is reinvested in JGBs, the chance is higher that the fiscal situation is sustainable. Most importantly, raising the consumption tax to 20% guarantees fiscal sustainability in most cases. Our analysis shows that without a consumption tax hike beyond the 10% rate, a fiscal crisis will be almost a certainty, even with a real economic growth rate of 2% despite a shrinking labor force. A reasonably quick hike of the consumption tax, namely a hike by 1% a year, up to 20%, combined with high or moderate economic growth rates, seems to keep the economy out of a fiscal crisis, where a moderate growth rate is defined to be generated by a productivity increase per working-age population of 1.9%, which was the average during the Koizumi years.