Anzu Natsuno, a student at an all-girls high school, witnesses her classmate Kana commit suicide after singing a mysterious melody in the auditorium. Days later, Anzu is approached by Riku Nagasei, a magazine columnist investigating the urban legend of the Densen Uta, or "infectious song," which is said to drive anyone who sings it to suicide. To test the legend, Riku persuades Anzu and her friends to sing the song.
