This is the largest association of Shinto shrines in Japan. According to its website, approximately 80,000 shrines are affiliated with this association, which has several branches throughout Japan. The member shrines regard Ise Shrine as the holiest of the Shinto shrines. They have also worked with the largest pro-constitutional revision group, Ustukushii Nippon no Kenpō o Tsukuru Kokumin no Kai, and collected signatures from visitors at some of the member shrines in order to make an appeal for constitutional revision. Utsukushii Nippon no Kenpō o Tsukuru Kokumin no Kai is officially a sub-group of Nippon Kaigi.
This is Jinja Honchō’s Tokyo branch. This branch is one of many that has actively collected signatures in support of constitutional revision. Here is their 2015 statement: they proclaimed their recommendation for the constitutional revision movement.
The website does not contain articles supporting constitutional revision per se, but it contains articles that cover many topics related to the constitution (such as the emperor system, Yasukuni Shine, the national anthem and national flag) mostly from a Shintō perspective. The group states that it respects Japanese traditions, especially the emperor system and Japanese language. This association describes itself as the only newspaper company for Shintō shrines (神社界).
Note: Without subscription, most of its articles are not available.
Kokusai Shūkyō Dōshikai | International Religious Fellowship
In 1947, the President of Dōshisha University, Makino Toraji, founded this organization with religious leaders from different religious groups. The groups included Konkō-kyo, Oomoto, Yasaka Shrine, the Roman Catholic Diocese of Kyoto, the Anglican Church in Japan, and Ittōen in Osaka. This organization does not officially take a political stance regarding constitutional revision, but they have occasionally had seminars about politics. In 2008, they had a seminar about constitutional revision. Information on the seminar is available here.
Nihon Shūkyōsha Heiwa Kyōgikai
This group has supported various anti-war and peace movements since 1962 and is against constitutional revision. This group is composed of “people with faith” from any religious group, including Buddhism, Shintō, Christianity and new religions. In 2015, they published a statement to criticize the Abe administration for its security bills. Their statements are available here.
Shinnihon Shūkyō Dantai Rengōkai | Federation of New Religious Organizations of Japan
Founded in 1951, this group has sought world peace and has organized memorial ceremonies for war victims. The federation is composed of new-religion believers, and they opposed Prime Ministers’ visits to Yasukuni Shrine on the principle of separation of government and religion. They published a statement to criticize the government for reinterpreting on Article 9 to enable Japan to enact its collective self-defense in 2014. The statement expressed apprehensions that the government would easily change interpretation on the constitution in the future, especially regarding the “freedom of thought, religion, and speech”, which this group is very focused on. The statement is available here. In 2015 and 2016, they also released a statement to express anxiety that the LDP’s 2012 draft loosens the separation of government and religion and emphasizes the state rather than individual freedoms and rights; find each statement here, 2015 and 2016). In 2018, the group held a seminar about constitutional revision with a lawyer from Asu no Jiyū o Mamoru Wakate Bengoshi no Kai, a young lawyers’ group that opposed the LDP’s 2012 draft. Information about the seminar is available here.
Shintō Seiji Renmei (Shinseiren)
This is a group related to Jinja Honchō, which was founded in 1969. According to their website, their mission is “correctly bequeathing Japanese history, culture, and traditions”. This group has called for constitutional revision, preservation and restoration of Shinto religious rites, and the protection of respects for the Royal Family. They have formally worked with groups related to Nippon Kaigi to support a national movement for constitutional revision, Utsukushii Nippon no Kenpō o Tsukuru Kokumi no Kai. Shinseiren also officially supports some politicians, including Yamatani Eriko. Shintō Seiji Renmei Kokkai Giin Kondankai (神道政治連盟国会議員懇談会) is a group composed of Diet members who agree with Shinseiren’s ideas.
Shūkyōsha 9-jō no Wa
This is a splinter group of 9-jō no Kai (9条の会). It is composed of people from many different religions that aim to prevent Article 9 from being amended. In 2013, they published a statement in protest of the Abe administration changing interpretation of Article 9 to enable Japan to enact its collective self-defense. The statement is available here. They have occasionally worked with other anti-war citizen’s groups, such as Sensō Sasenai 9-jō Kowasuna! Sōgakari Undō Jikkō Iinkai (戦争させない・9条壊すな！総がかり行動実行委員会).