While Shintoism may have had a permeating role in the past in Japan, in recent times it has slipped into the background. In earlier times, Shinto was very animistic - Shintoists worshipped nature through the sun, trees, water, mountains, etc. There was no particular line between man and nature, they viewed everything as one (much like the concept of brahman).
In addition, Japanese philosophy is that a person never had to adhere to one specific religion. According to japan-101.com, "Premodern Japanese were usually both Buddhists and Shintoists at the same time and often Confucians as well."
While it has faded into the background, Shintoism is still alive and well at festivals and on certain holidays by shrines who have specific importance. Also, the traditional Japanese love of nature has not faded, and derives strongly from Shintoist concepts. While very few Japanese today are traditional Shinto practitioners, the soul of the religion still lives on in Japan, seemingly immovably intertwined with Japanese culture.
Source used: http://www.japan-101.com/culture/culture_religion_shintoism_today.htm