^
H!P only sponsors it's own team, Gatas. Skylark Group is a restaurant chain that sponsored Gatas and organized several tournaments in the beginning before there was any league. Korenaga and another H!P Egg named Miyuki Kawashima were specifically auditioned for their futsal skills to act as "ringers". Kawashima later quit in early 2005. The Sphere League was started later that year for the idol/celebrity teams. Several tournaments would be played and whichever team racked up the highest number of points overall would be league champs. Each team was allowed to have one ringer (Korenaga for Gatas, Kajima for Carezza, Utsuki for Team Dream, etc.) The ringers are usually the ones chosen for the All-Star team, which played against better, non-league teams (high school, college, clubs). The Skylark Group League was started only recently. Along with Skylark, other Gatas sponsors, Addidas and JAL, have gotten involved by fielding teams of their own in this league, so presumably it's their way of keeping all the PR time to themselves while Gatas rebuilds. I wouldn't be surprised to see the two leagues play eachother in the future like the NFL and AFL since all the sponsorship is tied together in one way or another.