After defeating all five Team Star bosses, Cassiopeia revealed that she was Team Star's "big boss" and invited you to meet at the academy's schoolyard after dark, where she reveals her identity to you

"Heh. This must be quite a shock for you. The big boss... Cassiopeia... They were both me all along. When I saw you make quick work of those Team Star lackeys outside school that time, the idea for Operation Starfall suddenly came to me. My skills let me get hold of as much LP as I want, so I decided to use that to tempt you to helping me out. After the operation started, I kept an eye on you as a member of the "supply unit"... And I had you battle the bosses on my behalf. All for the goal of defeating me and putting an end to Team Star once and for all. But still...there's a part of me that wants Team Star to live on! I can't just roll over and let you win without putting up a fight! This is the final showdown. Are you ready?"