Kagami no Naka no Parallel Girl

 is the ninth single by X21.

CD Only Edition CD

 * 1) Kagami no Naka no Parallel Girl (鏡の中のパラレルガール)
 * 2) Holy☆Holiday
 * 3) Dear. Darlin’
 * 4) Kagami no Naka no Parallel Girl (鏡の中のパラレルガール) (Instrumental)
 * 5) Holy☆Holiday (Instrumental)
 * 6) Dear. Darlin’ (Instrumental)

CD+DVD Edition CD

 * 1) Kagami no Naka no Parallel Girl (鏡の中のパラレルガール)
 * 2) Holy☆Holiday
 * 3) Kagami no Naka no Parallel Girl (鏡の中のパラレルガール) (Instrumental)
 * 4) Holy☆Holiday (Instrumental)

CD+DVD Edition DVD

 * 1) Kagami no Naka no Parallel Girl (MUSIC VIDEO)
 * 2) Kagami no Naka no Parallel Girl (MUSIC VIDEO Off-shot)