The Japanese are very sensitive, especially middle-aged and older people. They will be annoyed if you ask them about their political life and religious perspectives. Questions about which party they support or what religion they follow should never be asked.
The Japanese King, the Mikado, and the Royal family are extremely respectable and sacred to the Japanese people. Therefore, the fastest way for you to be hated (or even beaten) in Japan is to do or say something which offends their Mikado and the Royal Family.
Moreover, you should never ask a Japanese about his income, which is considered very rude behaviour. Like in many other countries in the world, you shouldn’t ask a woman about her age and weight. You should also be aware that the Japanese are usually very reserved and they do not want to talk about their private lives. Although you may meet some exceptions, most Japanese people don’t like to start conversations with strangers.
It’s really great if you are invited to the home of a Japanese family for a meal. You should always take off your shoes before entering their house and when inside, avoid looking into their kitchen unless you are a really intimate friend of the family. You should also remember that Japanese people do not kiss or caress a child unless they are family members. Therefore, do not kiss or touch any Japanese child you meet, because it may annoy Japanese adults.
The Japanese are very superstitious. They always avoid anything related to the numbers 4 and 9 because in the Japanese language, “4” is pronounced like “death” and “9” is the same as “grief”. In Japanese hotels, they even don’t have rooms numbered 4 and 9. When dealing with Japanese people, avoid anything related to those numbers.