It's as if you said, "what is the difference between the English and the French?" or "the Germans and the Italians"? (there're all whites!no?) Asian people too think that western people all look alike. The same way as western people think that all Asian people look alike(there're all yellow!).
Although there is more or less a common culture between the two countries (confucianism, buddhism), the same way as the English has a common culture with all the europeans (christianism, roman and celtic culture...).
Nevertheless, there're a lot of differences (as between one european country and another):
- The two languages are absolutely different, except for the writing. but even in the writing there're many differences though.
- their cultures are different. Observe costumes, dramas (theater), armours, paintings, scuptures, traditional ceremonies, and you'll see that there are so many differences.
- we can sometimes see the difference between the japanese people and the chinese people (on the face). japanese are generally more pale.
- mentalities are different. japanese are tidy and clean, chinese less. the japanese are serious and austere, the chinese are more emotional and gesticulator, i'd say
- political regimes are different: japan is capitalist, china is communist.
- never say a chinese that he is japanese! because chinese and japanese don't really like each other you see...
But before wondering what are the differences between those two countries, it's better to wonder first if there're common points? and you'll see that both are thoroughly different. Indeed, they've more differences than they have common points.....