39

Background
This song was uploaded on July 27th, 2012, in celebration of Miku's 5th Birthday, and has reached over 600,000 views since. The song is about Miku giving thanks to all her listeners, people who use her, and just any overall fan of Vocaloid in general for sticking with her for this long.

This song is featured in the upcoming video game -Project DIVA- F as a non-playable song in the Live Stage mode.

Trivia

 * "39" can also be read as "Mi-ku", or "Miku"