As an island nation shut off from the rest of the world for a long time (with mild exceptions from China and Korea), Japan is very homogeneous. Almost 99% of the population is of Japanese ethnicity. The largest minority are Koreans, around 1 million strong, many in their 3rd or 4th generations. There are also sizable populations of Chinese, Filipinos and Brazilians (mostly descendants of Japanese, the Japanese-Brazilian, also known as Nikkei). Though largely assimilated, the resident Chinese population maintains a presence in Japan's three Chinatowns in Kobe, Nagasaki and Yokohama. Indigenous ethnic minorities include the Ainu on Hokkaido, gradually driven north during the centuries and now numbering around 50,000 (although the number varies greatly depending on the exact definition used), and the Ryukyuan people of Okinawa.
The Japanese are well known for their politeness. Many Japanese are thrilled to have visitors to their country and are incredibly helpful to lost and bewildered-looking foreigners. Younger Japanese people are often extremely interested in meeting and becoming friends with foreigners as well. Do not be surprised if a Japanese person (usually of the opposite gender) approaches you in a public place and tries to initiate a conversation with you in somewhat coherent English. On the other hand many are not used to dealing with foreigners (外人 gaijin) and are more reserved and reluctant to communicate.
Visibly foreign visitors remain a rarity in much of Japan, and you will likely encounter moments when entering a shop causes the staff to seemingly panic and scurry off into the back. Don't take this as racism: they're just afraid that you'll try to address them in English and they'll be embarrassed because they can't understand or reply. A smile and a Konnichiwa ("Hello") often helps.
