The situation in Japan is finally stable enough to analyze.
Our last major look at Japan introduced some of the larger parties. Importantly, it introduced us to the fluid nature of politics in Japan.
Unfortunately, due to that, any introduction will not last more than one general election cycle. As such, lets get right down to business.
Liberal Democratic Party
The LDP has been governing Japan nearly nonstop since the end of WW2. A small break of a year in 1993-1994 from government at the behest of an 7 party alliance was beat by an outright election loss in 2009 to the Democratic Party of Japan, which removed the LDP from government for a full 3 years. The party is generally Conservative in nature but has what we would consider a "red tory" philosophy on certain issues.
New Party Komeito
Oddly, the party is the "political wing" of the Soka Gakkai buddhist religion. The party has evolved over the decades and currently is generally conservative. Officially the party stands up for the "little guy" and it is known for various anti-corruption stances, but in the context of politics in modern japan, it is seen as a potentially permanent jr partner to the LDP.
Evolving from the Democratic Party (different name in Japanese) this party recently decided to plunge into the right opposition coalition. The Democratic Party itself is a mish-mash of various old parties that manged to win in 1993. Of the 7 parties that formed a short lived coalition, 5 eventually joined into the Democrats in some form. That alliance, and the party, are the only forces to defeat the LDP since the end of WW2.
This is the successor to the Restoration party, a right-wing alternative started in 2012 by a Tokyo Governor. The party quickly grew popular in Osaka after merging with the mayor's party there. Osaka and Tokyo are among the largest urban areas in Japan, and contain many seats. The party remains popular in the Osaka region.
Party of Hope
Formed by current Tokyo governor, Yuriko Koike, the party has the support of Komeito on the Municipal level. Two thirds of the Democrats in Parliament have joined the party for this election, and the entire legal Democrat Party will be fighting under this banner
This splinter group contains a third of the Democrats in Parliament. Many of them were rejected as being too 'left' wing for the Party of Hope, and others refused to work with a right-wing party. The party now finds itself in an working with other left parties due to its opposition to moves by the Prime Minister to increase the military.
Social Democratic Party
Once known as the Socialists, this party was the main opposition to the LDP for decades from the end of WW2 to the 1993 election. It, along with Komeito, were among the 7 parties to form a coalition government that year. The SDP however was able to work out a deal with the LDP that saw it head a coalition government from 1994 to 1996. The party has grown very small in recent years, and can only be expected to take a small handful of seats.
Japanese Communist Party
The JCP has been on the upswing in recent years due to moves by the Prime Minister to change the Constitution of Japan, as well as various trade and economic policies. The JCP now unofficially leads the left opposition coalition in the election and can be counted on to keep its two dozen or so seats, if not increase that number.
Current polls suggest the following:
300 - Gov
120 - Right
35 - Left
10 - Others
The main battle will be between Shinzo Abe, Prime Minister, and Yuriko Koike, the Governor of Tokyo. While Koike has rejected suggestions she will become the first female PM of Japan should her alliance win, she currently has momentum and is popular with the voters.
While the parties have shifted around quite a bit in the past few years, the general split between the government, the centre and right opposition and the left opposition has not. One of the LDP's key strengths is its ability to win single member seats. Japan uses a parallel proportional system where parties are assigned seats from the proportional list based on their vote totals. Should the LDP win 50% of the vote in any particular region, they will get 50% of the list seats, irregardless of if they've won every single member seat in that region or no single member seats in that region.
The Right has a possibility of causing problems due to support in the major cities, however it remains to be seen if this is enough to defeat the LDP.