Yoona is a public spy--she is a spy in a team of four (Sunny, Yuri, and Taeyeon) and they do good for the public. Then one day, Siwon appears. He and Sooyoung lures Yoona into coming into their academy, Zchenny [Spy] Academy and leave Ribet Academy. Yoona questions why. Sooyoung answers that doing good for the public isn't being a real, true spy; Yoona isn't a spy. She is a hero. But if Yoona really wants to be a spy, then she has to be secret. At Zchenny Acandemy, you do REAL missions. SECRET missions. DANGEROUS missions. Yoona finally thinks she is a real secret spy! But what happens when she falls in love with SIwon? And Siwon and Sooyoung betray her?