雲の遺跡 (Kumo no Iseki)

Background
Relics of Cloud was first uploaded on November 26th 2011, sung by Hatsune Miku and Meiko. It did not get many attention, with over 20,000 views (a revised version uploaded a month after of it, reach 200,000.). Yanagi-P then uploaded a Len version of the song on December 29th 2011, which reached over half a million views.

Len's version was more preferred, with more derivatives to it, and it's also featured in Exit Tunes compilation album "Vocalostar".

On July 10th 2012, Yanagi-P uploaded another version entitled "Relics of Cloud (Alternative)" with Meiko as the main vocals, and also a rearrangement of it (far different than Miku and Meiko's version, and also different from Len's). The Meiko version was one of the tracks uploaded for the Meiko-only compilation "AKA-TSUKI".