Professional football in Japan has a relatively short history. The J.League’s first tournament was organized in 1992, less than 30 years ago.
Especially before professionalism (but still true today!) football is seen as a sport discipline more than a popular phenomenon or a culture. It is widely practiced mainly at schools and companies, in fact the great majority of the Japanese professional clubs were born out of big brands, such as Panasonic, Hitachi, Toyota, etc.
Postwar Japanese society is built on the concept of “wa”, which can loosely be translated as “harmony”. Football is no exception: while passions can run high, rivalries are mellow, there is great respect for the opponents, and hooliganism is very rare and severely punished.
Most Japanese will follow a specific “genre” of football only: the local league, the European leagues, the national teams, high-school/university football, or women’s football. For instance, some J.League fans might go to the stadium every week and know everything about Japanese domestic football, but they might have not ever seen a Fulham FC game, or not even know that it exists!