Japanese religion is a complex beast; instead of believing in a single religion, different religions co-exist in peace. The main religions are Buddhism and Shintoism.
Shintoism only exists in Japan. It is a nature-based religion. Kami are the central objects of worship for the Shinto faith. Kami (神) is the Japanese word for god or gods. For instance there is a god of water, a god of fire etc.
Buddhism is based on the ideas of the Buddha and generally a religion that focusses on calmth and peace. Buddhists strive to attain freedom from suffering — otherwise known as nirvana — through a path of ethical conduct, wisdom and mental discipline.
Every city has a ton of shrines (Shinto) and temples (Buddhism). It’s good to know the difference between the two - as there are different customs to the different religions. For instance, at a Shinto shrine it’s customary to wash your hands whereas at a Buddhist temple it’s not. But things can get confusing if you encounter a Shinto shrine in a Buddhist temple!
At a Shinto shrine, first you should wash your hands using the provided water scoops. Then you go up the shrine to pray. You give an offer, usually a small amount of coins. The amount is not important. If there is a bell at the shrine, ring the bell to call the gods. Then make two deep bows, make your wish, and clap twice. After this make one more deep bow.
Christianity in Japan
There are few Christians in Japan - fewer than 1% in a country with 126 million people (July 2014).
In Nagasaki there are more Christian churches than any other place because historically it’s a port town where Portuguese missionaries arrived. Christianity in Japan is a complex story, where more than once Christianity was outlawed and Japanese catholics where brutally tortured and killed for their faith. These days there is full religious freedom.
It’s difficult to overstate how much the writings of Confucius impacted Japanese culture. Confucius was a Chinese philosopher who lived around the year 500 before Christ. Confucianism is not a religion; rather it is a set of norms and ethics.
If you visit Japan you will find that things are quite a bit different than in Western Europe or the US. The way people think and act is, in a lot of ways, very different. For example, in Analects 2:3 Confucius said:
Sign urging you to do the right thing.
“If you lead the people with administrative injunctions and put them in their place with penal law, they will avoid punishments and continue without a sense of shame. But if you lead them with excellence and show them their station through roles and rituals, they will develop a sense of shame and order themselves harmoniously.”
You will often find that signs won’t actually “forbid” you to do anything but urge you to do the right thing. So instead of “Don’t throw anything out of the window. $300 fine.” you will find a sign that says “Don’t throw anything from the window as it may hurt bypassers.” with a picture of a pedestrian getting hurt.
The culture is to urge you to do the right thing, with a focus on shame if you don’t do what is supposed to be right.