Shinto and Buddhism are Japan's two major religions. They have been co-existing for several centuries and have even complemented each other to a certain degree. Most Japanese consider themselves Buddhist, Shintoist or both.
Religion does not play a big role in the everyday life of most Japanese people today. The average person typically follows the religious rituals at ceremonies like birth, weddings and funerals, may visit a shrine or temple on New Year and participates at local festivals (matsuri), most of which have a religious background. Use your Japan cellular phone rentals to find a place of worship near you.