The religion that doesn't have a core group of sacred scriptures is Shinto.
Shintoism is the name of the native religion in Japan. It is based on the veneration of the kami or spirits of nature. Some kami are local and are known as spirits or geniuses of a particular place, but others represent larger natural objects and processes, for example, Amaterasu, the goddess of the Sun.
It is a religion that has very few sacred texts, and does not base its beliefs on what emanates from them but on beliefs rooted in the nature of things.