The Communist Party of Japan challenges the mainstream.
For example, it boycotted a ceremony to commemorate the Emperor, complaining that the government was using him for political purposes.
Sometimes the media focus is on a Communist politician named Keiji Kokuta, 72, who leads the party in the parliament, or Diet, in Tokyo.
He recently challenged the government over its handling over the diplomatic dispute with South Korea. His comments were translated and reported sympathetically in the Korean media.
Mr Kokuta also took up the cause of LGBT people in Japan, following discriminatory remarks about same-sex couples made by a politician close to Shinzo Abe.
Mr Kokuta has made it clear where the Communist Party stands on the most pressing political issue of the current era.
He says that it firmly opposes any form of revision to Japan’s constitution and wants to keep the current one as it is because – in his words – it “reflects the will of the people.”
There are around 300 thousand members of the Communist party in Japan. Because of the proportional representation system, it has a total of 25 representatives in the Japanese parliament, or Diet, led by Mr Kokuta.
That’s not a large number out of a total of around 700 MPs, but it does give the Communists a voice. Mr Kokuta sits on the influential Foreign Affairs and Defence committee.
He has become skilled at asking awkward questions to the Defence Minister and former Foreign Minister, Kono Taro.
In particular, he challenges signs of Japan’s animosity towards Communist China.
The issue of constitutional reform is the main focus of the current session of parliament, which began in Tokyo this week.
Mr Kokuta and his fellow Communists will vote against Prime Minister Abe’s plan to change the part of the constitution which relates to defence.
Mr Abe wants a new clause which would enable the Self Defence Force to operate more like a regular army, with the capacity to fight abroad in support of foreign allies, such as the United States.
To change the constitution, Mr Abe requires a two thirds majority in favour of reform in both the upper and lower houses of the Diet, before the issue is put before the public in the form of Japan’s first ever referendum.
And the Japan Times points out that as things stand, the pro-revision camp does not have a two-thirds majority in the upper house.
Other small parties may shift their position in return for political favours from the prime minister but Mr Kokuta’s camp will no doubt stand firm.
Mr Kokuta has represented people from Kyoto in the national parliament since the early 1990s.
He’s a popular figure and nurtures friendships in the ancient city. For example, last week he spent the day having his picture taken with elderly people who had been drawing pictures and doing calligraphy.
His website also contains a charming report about the Japan Hair Museum in the Gion district of Kyoto, established by a hairdresser called Tetsuo Ishihara.
Mr Ishihara is one of the few men who has mastered the skill of tying hair pieces for geisha.
I don’t suppose that Mr Kokuta and Mr Ishihara share the same commitment to left wing politics.
But in Japan, friendships between people often develop due to mutual respect, even if their perspectives on politics differ significantly.