Park Dong Ju is a spoiled, rich boy sent to a neighborhood school after failing his exams in a private school. He is stubborn, rude and mean, but has an extraordinary gift when it comes to music. He is disliked by many students and teachers, and is almost expelled when he played a prank on a classmate that lands him in a hospital. However, Hyung Wong, the principal, senses much potential in him and gives him another chance. He meets Bae Suzy, an independent girl who lives without parents when they died in a car accident years ago. They originally detest each other, but eventually, a strong bond forms between the two, changing Dong Ju in ways he had never imagined. She brings out the polite, softer side of him when he brings out the feistiness and warmth in her. But when he realizes that Suzy is distancing herself from him, he goes all out to seek the reason why, only to find the horrible truth that will strain their relationship and test Dong Ju’s limits. As Suzy’s condition worsens, Dong Ju starts to feel helpless and depressed; for she was the reason, he had changed. He begins to play music to vent out his feelings, and is noticed by a mysterious senior Lee Yoon Sung, who can’t help but notice his pain. Yoon Sung suggests that Dong Ju perform in a talent show. Originally thinking that Yoon Sung had suggested him to perform on television because of his talent, he refuses at first. But then he realizes what Yoon Sung had said and considers it. Dong Ju asks why Yoon Sung is helping him, but receives no answer. It is later revealed that Yoon Sung is actually Suzy’s childhood friend when they were little. Rarely leaving Suzy’s side, Dong Ju cannot play his melody for her as she cannot leave the hospital. Realizing this, he decided to listen to Yoon Sung’s advice and plays for her on a talent show while she watches with pride and sadness in her hospital ward. When he returns from the show later, he is devastated to discover that Suzy had passed away in her sleep and he manages to catch a glimpse of her body being wheeled away to the morgue, covered in a white sheet. He begs the doctor to let him see her body one last time, and seeing the raw pain on his face, agrees, but warned him not to take long. Dong Ju staggers to her body and sends the nurses away for privacy. He crumbles, falling to the ground before her body and cries.

“Suzy-ah, why are you doing this to me? You—you’re not dead yet, aren’t you? This is all a joke, right? You’re not…gone. You can’t be. What am I going to do without you?” he asks tearfully.

He then caresses her face and her hair, telling her to wake up, but she won’t. The nurses enter and wheel her body away. Dong Ju chases after her body, but is stopped by the doctor and Yoon Sung. When he had calmed down, Yoon Sung tells him to leave so that he would rest, but he refuses, saying that Suzy is not gone yet and he will wait for her. Dong Ju starts to get angry again and lashes out at Yoon Sung instead.

“If I hadn’t perform, I would have been with her. This is your entire fault! You told me to perform!” he screams as he sobs.

Yoon Sung is outraged by his accusation and leaves, telling him that Suzy would not have wanted him to revert back to his old self just because she isn’t there to help him anymore. Dong Ju falters and stops crying, sliding against the wall and crumpling to the floor with a helpless and lost look on his face. He falls asleep and is awakened by a nurse who was tapping his shoulder. She passes him a note. He looks up at her when he realizes that it’s from Suzy. The nurse tells him to read it later, when he was outside. Dong Ju pockets the note, careful not to tear it. She tells him that her name is Lee Hee Seon, Yoon Sung’s older sister and that she had witnessed what had happened between Yoon Sung and Dong Ju. She also states that Suzy had watched his performance before she succumbed to her illness. Dong Ju cheers up a little when he hears this. Hee Seon advises Dong Ju to go home and rest as he can’t do much here and that he was scaring the patients.

Dong Ju gets to his feet and stumbles home dazedly, but ends up on a rooftop of their school; Suzy’s and Dong Ju’s favorite place to hang out. Falling to his knees, he starts to cry again.

“Why are you doing this to me? You said you would never leave me, then where are you now? Why did you leave me? Please don’t leave me. Please, I’m begging you,” he cries and whispers, “Please.”

He screams her name and remembers her note. He takes it out and imagines her writing the note, how her forehead would wrinkle when she was thinking hard, how she would nibble the pencil when she was confused. He starts to read the note, but can’t go on anymore as his voice breaks. He then hears her voice reading to him the note.

My Dong Ju,

These few months have been the best of my life. When I saw you perform on the T.V., I could not help but cry. When I saw you perform the song you had composed for me, I know that even if I die, you would still love me. When I fell sick, you came to visit me everyday, and stayed overnight on weekends, staying with me until the very end. I saw how tired you were, but you would still come, sometimes bringing me food so that we could eat together. I can see your pain as you tried to conceal it when you smile at me. When I think of you, I smile. I used to see you as a rude, mean boy you were when you first came, and now you are a polite, sensitive and handsome man. My Dong Ju is so handsome. I want you to know that I will never leave you. I am always with you, in your heart. Sometimes, when you think of me hard enough, you will feel my hand in yours. Sometimes, when you should miss me, just hum to yourself my melody and you will feel me next to you. Dong Ju-ah, promise you will never forget me.

Love you forever
Suzy

Dong Ju presses the note to his heart and he cries, promising not to forget her. He stands and watches the sunrise. He closes his eyes as he feels the breeze on his face and smiles as he feels her hand in his. He opens his eyes and looks to his right, and sees Suzy smiling at him.

Dong Ju is leading a successful musical career and Yoon Sung is his manager. His number one hit is “Suzy’s melody”, the melody he had composed for Suzy. Even though it has been almost six years, he still remembers her, claiming that she was his reason for music, and that she is his music. When the reporters ask where is she now, Dong Ju smiles and looks up to the sky.

“Who knows? But wherever she is, she will still be a part of me,” he points to his heart.

At night, he stands at the rooftop of his school again, and does the same on that very night Suzy died. He raises his face to the moon, closes his eyes and breathes in the scent of the night. He feels a hand in his and he smiles.

Opening them, he looks at Suzy and says softly, “You’re here.”

“Always,” she smiles.

“I will never forget you,” he says.

A tear streaks down her pale face. “Dong Ju-ah, I know.”

They look at the moon together, hands intertwined, reminiscing the past.

“I know,” she whispers.