"Adolescence" was first uploaded on December 26, 2008, in celebration of the Kagamines' first anniversary. It is a cover of Signal-P's hit, "Cendrillon", with different lyrics. Though Signal-P himself said that it is a cover (technically written as, "Cendrillon Kagamine ver."), it's still considered as a "Rin Original song" and "Len Original song", as tagged by Signal-P in the original video in Niconico.
It's featured in Signal-P's Exit Tunes compilation, "The best of Dios/Signal-P" as one of the tracks along with the original Cendrillon, as well as Signal-P's album "CYBER COMPLETE ～Nonstop SigMix～". It is relatively popular with over half a million views in NND, inviting various derivatives may it be PVs or fanarts.
In a matter of plot, Orange, the lyricist to the song, said that the theme is "at the age of 14, the duo celebrating adolescence". With only that to grasp, both Orange and Signal-P said that the song could be interpreted in any way; may it be lead to a rather famous interpretation on the duo being romantically interested with each other, or the refusal of having to grow up.
A hand-drawn PV done by Zashiki Usagi. The PV was released incomplete in 2009, and after 2 years the full version was finally released. This PV touches the topic of the conflict more explicitly, as it shows how the their fraternal love is in risk of twist into an incestuous relationship. Zashiki Usagi also published a short doujinshi which is available for reading in Pixiv.