The most prominent geographic feature of Japan is that it is a set of islands with mountainous interiors. The major good thing about this is that it makes it very hard for any foreign enemy to invade Japan. Japan has never been successfully invaded in historical times. (It would almost certainly have been successfully invaded at the end of World War II had it not surrendered after the US dropped atomic bombs on Hiroshima and Nagasaki.) Japan’s insularity has protected it from foreign invasion and domination. However, Japan’s small size and mountainous terrain limit it in some ways. Most importantly, Japan has few natural resources. This was a major negative in the early 20th century, leading Japan to push for an empire. This push helped bring about WWII.
A major positive feature of China’s geography is its two major rivers and the flat lands between them. These rivers made transportation relatively easy along an east-west axis in both the north and the south of China. The flat land between the rivers made it possible to dig the Grand Canal linking the two, greatly increasing China’s economic potential. A relatively negative feature of China’s geography is that most of its arable land is all in one area. This means that large areas of China have been unable to support dense populations and have typically been less economically advanced.