Love Phobia

Jo-Kang is a young boy when he meets a girl named Ari. Ari was unique and different than all the other girls. They instantly had feeling for each other and then Ari vanished. She appears later in his life to vanish again. When suddenly one day Ari appears again in Jo-Kang's life. Jo-Kang loves Ari and is curious as to why she suddenly disappears every time they see each other. Ari has a secret that she has been keeping. What is her seret?