There are two main religions in Japan (Shinto and Buddhism) that coexist together and complement each other.
Buddhism was introduced in Japan in the 6th century, but Shinto is the indigenous faith of the Japanese people. At the beginning, there were many conflicts between both religions. These days, it doesn’t seem to be a problem any longer; what’s more, some ceremonies (e.g., weddings) are often held in Shinto style, the others (e.g., funerals) in Buddhist style.
Apparently, Shinto is more popular in Japan. However, it looks to me like Shinto and Buddhism are “mixed” and people don’t really follow any of these two religious, but rather “follow the traditions”.