Sulli and Minho are secret agents. They have known each aother since kids. They both work for S.A.C. (Secret Agentcy Company). In one of there missions some thing went wrong that made Sulli lost her memory and get kicked out of S.A.C. Minho wasn't in that mission so he didn't know that Sulli lost her memory. When he finds out he starts searching and finds out that what made Sulli lose her memory was not an acident it was planned. Sulli for some reason gets back in S.A.C. but still

Suli is the staight A student and Minho is the playboy who never cares about his grades. Krystal is the new girl in class who only cares about her looks. Taemin is the cute, childish boy who only cares about what people think of him.   Sulli