Japan's Election Makes No Difference
Regardless of which party would have sealed a majority, the reality is the fact it would not matter in terms of of Japan's operation.
In 2009, the Democratic Party of Japan (DPJ) gave the ruling LDP a thrashing. The outcome was that even though opposition Yukio Hatoyama replaced the LDP's Taro Aso as Prime Minister the change made absolutely no difference to how Japan operated politically, diplomatically, or financially. What occurred is that those in power, the bureaucrats who hold their position for life which were likely inherited from family, simply brought government operation to a halt.
Many in the pension offices across Japan took up to 90 days to approve new pensions where before it took only 7 to 10 days. Bureaucrats in government ministries had projects cut or delayed. The Infrastructure Ministry intentionally held up bridge construction across Japan for over two years from 2009 to 2011. Both of these actions had their desired effect - make the DPJ look bad and undermine DPJ leadreship.
It worked, and the Tohoku Disaster in 2011 was seen as blessing for the LDP. LDP supporting bureaucrats held up emergency aid and funding for almost 6 months to victims of the disaster. This created rage among the victims who put the blame on Prime Minister Naoto Kan and later his replacement, Noda. This backlash brought the LDP back to power in elections in December 2012.
This is the reason that Sunday's election would make no difference. The bureaucrats who actually run the government would sabotage any victory by an opposition party.
Japan is owned and run by conservative bureaucrats who speak no language other than Japanese and know nothing about the world outside Japan. These men can be found in the ministries. They form the unelected government of Japan. These are the unelected and unappointed who, for instance, sit on the Education Ministry and preside over an English education system that produces graduates who place LAST in the world on the TOEFL IBT speaking section.
These are the same men who brought you Fukushima Dai-ichi, Monju and Tokaimura. These are the men who have turned Japan from one of the world's most beautiful countries into one of its ugliest, through the tools of concrete, dams, retaining walls and tetrapods.