Eternal Souls (AFS) - Prince of Tennis Fanfic

Allistar Academy. A school shrouded in mystery. Only those who have been invited can enter. No one knows why they hide themselves. Many say it was a school for the gifted. Yet some were just average and had no special talents at all. Oh were they wrong. Some say there was a different and specific piece that made all of them similar.
One day, 10 schools from Japan and 1 team from America were invited to this mysterious academy. Once they were there, they saw old friends who disappeared a few years ago. But hid secrets that would make the world turn against them. What kind of school is Allistar Academy and what secrets are they hiding?