You Know What? It's a Secret.

Jun-hyoung is a training teacher who meets Hye-na, a very outgoing student. She always acts freely with out any restriction. As time as goes by, she slowly starts to interfere in his life. Sun-shul, who is very lonely, loves Hye-na. Jun-hyoung feels that it's hard to put up with Hye-na, but his mentor insists and tells him to take care of her. Jun-hyoung does not understand and feels as though this situation in unfair for him. Soon after, he finds out Hye-na's secret...