The J-League is the Japanese Professional Football League, Asia's most succesful league started on the 15th May 1993 taking teams for the previous Japan Soccer League. The league started with just 10 teams, but it's instant success saw expansion to 16 teams by 1999 and another 9 teams in J-2 (a lower division).
Japanese National team shirts are here, if you want those rather than a club sides.
Coaches & players from Europe & South America came to the league in it's early days raising it's presence and quality, notable names include English striker Gary Lineker and French manager Arsene Wenger who was in charge of Nagoya Grampus Eight.
At the end of each season two teams from J2 are promoted to J1 and two are relegated the other way as long as the J2 clubs meet the requirements of a J-League franchise (revenue levels, stadium size, academy structure etc), clubs have tended to meet this requirements so far. In 2005 the league went from 17 to 18 teams, promotion was a normal but there was also a playoff between the 16th placed J League team & the third placed J2 team. This playoff structure remains in place and in 2006 the 16th placed team lost that playoff and were also relegated to J2, with three teams being promoted to the J-League for the first time.