||Japan is currently by far the most indebted nation in the world. Despite its debt being more than twice its GDP, current yields of Japanese Government Bonds are second lowest in the world. We decided to analyze the sustainability of current debt levels. We begin by analyzing the idiosyncratic properties of Japanese bond market that enables the government to borrow cheaply. Than we observe the shifts in domestic market conditions that could have negative impact on the current low yield environment. Furthermore, we perform sensitivity analysis of the sustainability model used previously and then modify it to observe shorter term risks associated with current debt levels. We compare the short and long term approach of sustainability measurement. Our findings confirm previous findings that Japanese fiscal policy is unsustainable in the long term. However, we have observed that current debt levels impact shorter-term risks much more significantly. Short-term risks have risen to such magnitudes that in case Japan will have difficulties to rollover its debt in domestic markets, the inability of Japan to pay yields demanded by foreigners will cause its default.