Sapphire Star Entertainment, founded by its CEO, Choi Siwon, have a decent amount of trainees. Of course, being a big entertainment company, Sapphire Star provides all the training but occasionally, trainers or even the CEO himself, sends trainees to train at the Cloud Arts Academy.

Cloud Arts Academy is a highly specialized arts academy with a vast array of teachers ranging from vocals to dance stunts and modelling. Owned by Kim Junghoon, the academy was aptly named for the curriculum may sound harsh but is actually pretty light like a cloud. Considering that its trainees and students have all become famous one way or another (famous balladeer Jung Leo used to be one of its students), Cloud Arts Academy stood for excellence and aiming for the skies. (It's main building is also a madhouse but that's another story.)