TONY JONES, PRESENTER: It's been described as one of the most influential political organisations in Japan. Nippon Kaigi, or Japan Conference, has an impressive list of members and advisors, including the Prime Minister and much of his cabinet. But very little is known about this right-wing nationalist lobby group which aims to reshape Japanese politics and policies and even change the Constitution. It operates mostly out of the public eye, but North Asia correspondent Matthew Carney gained rare access to file this exclusive story for Lateline.

MATTHEW CARNEY, REPORTER: A call has gone out and people from all over Japan have responded. To hear a vision from one of Japan's most powerful political organisations, the Nippon Kaigi. And it's back to the future. Nippon Kaigi want to restore the status of the Emperor, keep women in the home to nurture family and rebuild the might of the armed forces.

To do that, they have to scrap the pacifist constitution that was imposed by the Americans. This is the first step, they say, to shake off the shame of the defeat in World War II and restore pride.

YOSHIKO SAKURAI, JOURNALIST (voiceover translation): We need to ask ourselves: will the current constitution of Japan protect Japan and its people? The answer is no. We need a constitution that reflects the true Japanese identity.

MATTHEW CARNEY: The biggest champion to the cause and the group's specialist advisor is Prime Minister Shinzo Abe himself.

SHINZO ABE, JAPANESE PRIME MINISTER (voiceover translation): To create a constitution suitable for the 21st Century, that's where it needs to be spread throughout Japan. I seek your continued support on this. Let's move forward towards changing the Constitution.

MATTHEW CARNEY: The Nippon Kaigi has serious clout. The Deputy Prime Minister is also a member, as well as 80 per cent of the cabinet, as are almost half of all parliamentarians. It's a kind of uber lobby group that uses its 38,000 members to mobilise support.

The Nippon Kaigi has pledged to collect 10 million signatures by next April to change the Constitution. Some say it's a cult-like organisation.

KOICHI NAKANO, SOPHIA UNIVERSITY: I think it is, you know, cultish, in the sense that it's very sectarian. They have a very strong view of us and them. They have a sense of the inner group because they feel victimised, marginalised and they have been subjected to severe injustice, that they need to take back Japan.

MATTHEW CARNEY: But their spokesperson says they are only trying to normalise Japan.

AKIRA MOMOCHI, NIPPON KAIGI, STRATEGIC COMMITTEE (voiceover translation): It is proper for an independent sovereign nation to have an army. There are no sovereign nations without one. Armies are deterrents. They exist to prevent war. We'll keep our pacifist traditions, but we need to respond to the rising threat of China.

MATTHEW CARNEY: The fundamental vision for many in the group is to go back to a time when they say Japan was pure and free from foreign influence, like the Edo Period in the 16th to 18th centuries when outsiders were strictly forbidden and Japanese culture flourished. They believe this beautiful Japan has been lost.

HIDEAKI KASE, NIPPON KAIGI, TOKYO BRANCH: There are two Japan. One is traditional Japan and one is Westernised Japan. And we wish to revert to the traditional Japan.

KOICHI NAKANO: They are romantic, they are irrational, they live in their own world. So they lack strategic thinking in terms of what they are going for and for what reason and how does that serve national interest in realistic terms?

MATTHEW CARNEY: The darker side to the organisation is to deny any wrongdoing in Japan's war-time past. They assert World War II was one of defence, not aggression. They say comfort women were not sex slaves, but well-paid prostitutes and the rape and pillage of Nanjing in China that historians say killed up to 200,000 was a fiction.

HIDEAKI KASE: There was no massacre at all. That is an utterly false accusation.

KOICHI NAKANO: They try to rewrite history in order - and they think that this is fundamental to what they see as Japan's need to restore pride. They think that because the kids and the - you know, the adults of Japan are being brainwashed by self-blame and a sense of shame in their history.

MATTHEW CARNEY: Many in Japan think Nippon Kaigi's ideas are dangerous and have to be countered. Professor Setsu Kobayashi is one of the country's top constitutional experts.

SETSU KOBAYASHI, CONSTITUTIONAL EXPERT (voiceover translation): They're thinking about Asia before the war when Japan was the leader of Asia. They want to repeat that. They openly say that.

MATTHEW CARNEY: On his Friday lunchtime radio spot, he warns against reform of the Constitution, arguing it could lead Japan down the warpath. So far, Prime Minister Abe and Nippon Kaigi have succeeded in passing security bills that let the armed forces fight overseas again. Kobayashi says the move is unconstitutional.

SETSU KOBAYASHI (voiceover translation): The majority of people are not convinced. We have to fight and not give up, otherwise we'll live under a dictatorship. Freedom and democracy will not exist.

MATTHEW CARNEY: Professor Kobayashi was once a member of Nippon Kaigi, but is now one of its biggest critics. He tried to change them from the inside, but couldn't. As a self-described commoner, he says the organisation is one of elites, out of touch with the people. Polls consistently show that the majority of Japanese don't want the country's pacifist constitution to change.

SETSU KOBAYASHI (voiceover translation): They want to achieve the dream that Japan pursued pre-war to be one of the top five military powers in the world. To enable this, our country will go around the world fighting wars alongside the Americans. Mr Abe went to the United Nations and said that Japan will seek aggressive peace; militarism is another name.

MATTHEW CARNEY: Professor Kobayashi now devotes much of his time fighting the Nippon Kaigi and the reform of the Constitution. He believes it's a battle for the very hearts and minds of the Japanese and the outcome will decide the country's future. The Nippon Kaigi say their ambition is to simply protect Japan and its identity.

AKIRA MOMOCHI (voiceover translation): It is a difference of opinion. We want to retain the Japanese traditions, to make Japan as it should be. We have the power to do it.