Shinto is the traditional, indigenous Japanese religion. Buddhism, also practiced by nearly all Japanese, did not arrive until around 650AD. Most Japanese participate in both religions, but today, Buddhism tends to be responsible for deaths and funerals, because it has more to say about the afterlife (and because Shinto views death and dead bodies as poluting - not appropriate for their priesthood to deal with). Very few Japanese are Christian (about 1%), but many Christian Japanese also participate in Shinto rites as well.
Shinto is centered on `KAMI' (innumerable gods or spirits) of places, families, communities who interact with us. Kami are:
`The Four Affirmations' of Shinto.
1. Tradition and family must be honored.Shrines organize MATSURI (community festivals) about life passages (births, marriages, age 3-5-7 ceremonies, etc) celebration of family ancestors, etc. (Not much about death, however.) Each local community has its own matsuri traditions featuring colorful costumes, special dances, floats rolled or dragged through the streets, boats, bonfires, wrestling contests, etc.
2. Love of nature plays a great role. Most shrines are built in groves on the edge of the village, near a waterfall, near a distinctive rock on the seashore, etc.
3. Physical cleanliness must be assured before prayers or approach to a shrine. Lots of washing, sprinkling with salt, etc.
4. Festivals and ceremonies must be honored. Japanese festivals (matsuri) are joyous occassions with lots of energetic activity: eg, the young men in bright jackets pushing around a huge wagon containing the sacred shrine during a parade, wrestling matches (that is, sumo). These events are intended as entertainment for the benefit of the kami as well as for the participants.
Every small community has at least one or more `shrines' (jinja), maintained by a committee of prominent citizens of the community. The `sanctum sanctorum' is a small box designed like a house with small doors, etc.