The Japanese civilization, obviously, only has one country in it: Japan.
Japanese culture can be portrayed as a civilization that incorporates Western practices with Chinese culture, forming an unprecedented, unique fusion that is the defining characteristic of the Japanese civilization.
The volatile nature of Japanese relation with world power is an interesting conundrum in itself. Before modern history, Japan was best friends with China and depended on it very much. However, ever since Japan opened it doors to the Western world, it started to militarise and eventually went against the Western gone on to become the best allies of the US and is widely known to be US' stronghold, both politically and economically, in Asia.