Young-won and Sun-min attend the same high school and are best friends. Sun-min is an announcer for the radio club and has a lively and cheerful personality. Young-won, on the other hand, is introverted and quiet and is good at singing. One night, Young-won was practicing singing alone in the music classroom. Sun-min urged her to go home, but Young-won insisted on practicing singing, so Sun-min went home first. After Sun-min left the classroom, Young-won was startled to hear someone singing and immediately looked around, but she couldn't see anything, but she felt someone was watching her. The next day, Young-won didn't go to school. At noon, Sun-min was recording in the computer room when he suddenly heard a woman calling her name repeatedly in anxiety. Surprisingly, this voice was Young-won's voice. Strangely, although there were many students in the computer room, only Sun-min could hear Young-won's voice, and Sun-min fainted on the ground in fear. After Sun-min woke up, he felt that something was wrong. He couldn't avoid his friend's voice, and finally calmed down and listened carefully to Young-won's story. Young-won told Sun-min that she was killed, but she didn't know where the body was. Sunmin searched the entire campus, but he couldn't find any trace of Young-won. Sunmin began to suspect Hee-won, the music teacher who was always very kind to Young-won. That night, Sunmin and Young-won's ghost went to the music classroom to find the teacher, but the teacher was hanged in the classroom. One day, a classmate, Choa, told Sunmin that she knew Sunmin could hear Young-won's voice, and that she could hear the voice of ghosts since she was a child. Sunmin felt comforted that someone had the same experience as her. Soon, Young-won's horrible body was found in the basement of the school elevator, and the whole school was immediately shrouded in a shadow of terror.