Happy Appli

 is the third single by X21.

CD

 * 1) Happy Appli (ハッピーアプリ)
 * 2) Best Friend
 * 3) Happy Appli (ハッピーアプリ) (Instrumental)
 * 4) Best Friend (Instrumental)

Limited Edition DVD

 * 1) Happy Appli _MUSIC VIDEO
 * 2) Best Friend _MUSIC VIDEO
 * 3) Happy Appli _MUSIC VIDEO Off-shot