Anzu Natsuno (Yuko Oshima), a student at an all-girl high school, is walking in the hallway when she hears a mysterious melody coming from the auditorium. There, she finds her classmate Kana (Atsuko Maeda) singing and Anzu's soon shocked when she sees Kana committing suicide after the song ends.
A few days later, Anzu is approached by magazine columnist Riku Nagase (Ryuhei Matsuda), who explains that he's investigating an urban legend of Densen Uta, or the infectious song, that turns whoever sings the song suicidal. Riku convinces Anzu and her friends to sing the song to see if there's any truth to the urban legend. They reluctantly agree and sing the song.
Over next few days the girls, one by one, kill themselves, leaving Anzu to fight for her life. Coming closer to the source of the song, Anzu finds out about an unimaginable secret relating to her past and the song.
