One of the early original Miku songs. A mysterious letter falls from the sky. There are only spaces and line feeds on the letter, but somehow the girl can read the message. Led by the message, unheard voice and unseen man, the girl keeps looking for "something unseen". The original title was I composed a song with the theme "a letter falls from the sky". Soon after the release the author changed the title by a suggestion from a viewer. This song is featured in the album Hatsune Miku Best ～memories～ (初音ミク ベスト～memories～).