In most democracies the prospect of a change of government following a general election is seen as part of the normal political process, but in Japan this has not been the case. Elections are not rigged in Japan. Procedures for voting and for counting votes are meticulous. There have been problems of malapportionment between different electoral districts but this has hardly been the principal cause of long-term LDP rule since the 1980s. Japan is unusual in combing a democratic and reasonably fair electoral system with the political dominance of a single party for a longer period than in other modern democracy.
J.A.A.Stockwin, Party Politics in Japan, in Takashi Inoguchi & Purnendra Jain ed. Japanese Politics Today: from Koraoke to Kabuki Democracy. Palgrave Macmillam 2011. page 90.
the road not taken 