Junho and Hyoyeon met each other at a Party and they spend time together and realised that they started to like each other. But they don't know that their Parent's companies are competitors and that they hate each other. 

Hyoyeon:

daughter of the Kim's

wants to become a professional dancer

loves Junho

Junho:

the only son of the Lee's 

the heir of the company

loves Hyoyeon

2PM: 

Best Friends of Junho

Minjun is Hyoyeon's brother

Sunny&Sooyoung: 

Hyoyeon's best Friends