This rock island is famous for its ritual of the Kozagawa Kochi Festival (An Intangible Folk Cultural Property designated by the nation). The three main ships which leads the festival are ancient rite whale ships decorated like a battleship. Kochijima Island which is made of granite porphyry of the Kozagawa arc-shaped dike, is the Shintai (the object of worship believed to contain the spirit of a deity).