The Shinwa-kai has been based in Takamatsu, Kagawa ever since its formation, and the only designated yakuza group based in the Shikoku region. The Shinwa-kai is one of the four designated yakuza syndicates active in Kagawa Prefecture, along with the Yamaguchi-gumi, the Sumiyoshi-kai, and the Kyodo-kai.
Since 1996, the Shinwa-kai has been a member of an anti-Yamaguchi federation named the Gosha-kai, along with four Chugoku-based organizations, the Kyosei-kai, the Kyodo-kai, the Goda-ikka, and the Asano-gumi.
- "Police of Japan 2011, Criminal Investigation : 2. Fight Against Organized Crime", December 2009, National Police Agency
- "2010 Police White Paper Chapter 2 : Furtherance of Organized Crime Countermeasures", 2010, National Police Agency (Japanese)
- "1993 Police White Paper Chapter 1 : The Actual Condition of the Boryokudan", 1993, National Police Agency (Japanese)
- "The Shinwa-kai re-registered as a designated boryokudan", 11 December 2010, Shikoku Shimbun (Japanese)
- "Boryokudan condition in Kagawa Prefecture", October 2010, Kagawa Prefecture (Japanese)
- "The Fourth Kyosei-kai", 20 February 2008, Matsue Joho Center (Japanese)