The Japanese political system has conventionally been perceived as a parliamentary system, which indicates that executive power depends on the national assembly. Such a parliamentary system could with coherent governing parties show decisive power in the policy-making processes. After the political reforms were implemented in 1994, some prime ministers did indeed show such decisive power in Japan, and presently the prime minister enjoys almost a free hand. At present the problem of Japanese politics arguably lies on an excessively powerful prime minister. Having said that, prime ministers in Japan had changed almost every year between 2006 and 2012; this office had symbolised the instability of the Japanese political system. The mystery of the Japanese political system merely deepens, when these observations are considered. This paper explores the question as to why such an extreme alternation of prime-ministerial power occurs in Japanese politics. By so doing this paper depicts the nature of the political system in Japan.