Yakusoku no Oka

 is the seventh single by X21.

CD+DVD CD

 * 1) Yakusoku no Oka (約束の丘)
 * 2) 3 Dome no First love (3度目のFirst love)
 * 3) Who is X!?
 * 4) Yakusoku no Oka (約束の丘) (Instrumental)
 * 5) 3 Dome no First love (3度目のFirst love) (Instrumental)
 * 6) Who is X!? (Instrumental)

CD Only CD

 * 1) Yakusoku no Oka (約束の丘)
 * 2) 3 Dome no First love (3度目のFirst love)
 * 3) Yakusoku no Oka (約束の丘) (Instrumental)
 * 4) 3 Dome no First love (3度目のFirst love) (Instrumental)

DVD

 * 1) Yakusoku no Oka (MUSIC VIDEO)
 * 2) Yakusoku no Oka (MUSIC VIDEO Off-shot)