ヒカリ (Hikari)

Background
The song is a duet between Hatsune Miku and her genderbend (lower pitched male version of her), Hatsune Mikuo. In the song, Miku tells of how she sings songs of loneliness. Hearing her song, Mikuo is touched and yearns to stop her tears, and through a miracle becomes solid. Finally no longer alone, Miku happily sings with Mikuo, thankful for the companion that she has come to depend on. However, she begins noticing how the world around her changes, with time eventually coming to a stop. It is then revealed that the VOCALOID software they live in has encountered a bug, and the system must restart. The user restarts the program and, as a result, Mikuo is deleted from existence. Miku watches as he disappears, her heart broken that she can not comfort him anymore.

The song was released in celebration of Hatsune Miku's birthday.