ased on a Japanese manga, "Kanna-San, Daiseikou Desu," this story revolves around Kang Han-na (Kim Ah-jung), an overweight phone sex employee and secret vocalist for Ammy, a famous Korean pop singer who actually lip syncs as she cannot sing. After getting humilitated publicly by an ungrateful Ammy, Han-na undergoes an extreme makeover to become a pop sensation herself.

Overview from themoviedb.org