Contrasting the “Shōjo Tsubaki” song with other musical cues in ero-guro media (e.g., the carnivalesque themes in Urotsukidōji or the silent tableaux in Kansen ) reveals its unique function. Where other works use jazz or dissonant industrial sounds to evoke modernity’s decay, the Shōjo Tsubaki song uses the shōka (school song) style—a nationalistic, innocent form. By corrupting this specific genre, Maruo and Harada critique the failure of the Japanese post-war family structure and the myth of nostalgic innocence.
The film opens with a song (often simply referred to as the Opening Theme or Shoujo Tsubaki ) performed by a child-like voice. The lyrics are deceptively cute but carry a dark double meaning in the context of the story.