Japanese religious life is often described as syncretic rather than exclusive: most people participate in both Shinto rites, such as New Year shrine visits and life-cycle blessings, and Buddhist rites, especially funerals and ancestor memorials, without treating these as competing exclusive identities, which is why survey figures vary enormously depending on whether they measure formal affiliation or ritual participation.
Pew Research's Religious Composition of the World, 2010-2020 places a large majority of Japan's population in the religiously unaffiliated category by strict self-identification, even though most participate in Shinto and Buddhist observances. Shinto, Japan's indigenous tradition centered on kami, spirits associated with natural features, ancestors and local shrines, has no single founder or scripture and was formally separated from the state after 1945, having been mobilized as State Shinto to underpin nationalist ideology and emperor worship from the Meiji era of 1868 through the Second World War.
Buddhism arrived from Korea and China in the sixth century CE and developed distinct schools, including Zen, Pure Land and the esoteric Shingon school founded by Kukai in the ninth century. Christianity, introduced by Jesuit missionaries in 1549, was violently suppressed under the Tokugawa shogunate from the 1620s until religious freedom was restored in the Meiji era.