Kung Fu is just a part of the chinese martial art. In china, martial art has developed to an extremely complicated level, even the hand shape can consist of dozens of different type to cause different damages. Nobody knows, i believe, how many kinds of martial arts exist in china. As for japenese karate, ninjutsu etc, they were all derived from chinese martial art with japenese own development. From chinese Tang Dynasty( about 1700 ys ago), japenese has imported a huge amount of chinese cultrue into their own, like chinese character, music, art of tea, and martial art etc. Do you know the city of kyoto (japenese ancient capital) is an exact copy of the capital city of then Tang Dynasty, Chang An. That is why people always say japenese culture is a little brother of chinese culture.