"Meltdown" is an original song by iroha(sasaki) and is his most popular work. It's also widely considered Kagamine Rin's most notable song.
There are various interpretations of this song. The PV can be literally interpreted as Rin jumping into a nuclear reactor to commit suicide, or it can be interpreted figuratively as Rin trying to get rid of her past or purge herself of her sins in order to grow up and become an adult.
Iroha has said the lyrics and video represent conflicts in the singer's inner psychological world. In the video, Rin jumps into a reactor core/nuclear reactor and chokes someone, possibly to death. The little Rin stands for innocent childish mind inside her. The choking scene symbolizes erasing her past self and starting anew.
There was a controversy over the video and the Weekly Vocaloid Ranking on Nico Nico. Taking advantage of the Vocaloid Ranking's score system, people made dummy accounts and put the song on their My List just to increase the song's score in the ranking, making it stay in the top 20 indefinitely. Though iroha(sasaki) asked his viewers to stop this illegitimate practice, they did not stop and in retaliation, Iroha deleted the video from his account and put it up on Nagimiso.SYS's. This disqualified the video from being in the rankings, as one of the requirements is that the original composer must submit it.
This raised awareness about the cheating behind the rankings. The score system was modified, thus taking many long-lasting regulars such as "Hatsune Miku no Shoushitsu", "Miku Miku ni Shite Ageru", and "World is Mine" off the list altogether.
The new PV put up on Nagimiso.SYS's account features several touched-up areas including a different-looking reactor, new countdown text, and added detail in certain scenes.
A techno remix by baker of Kagamine Rin's original "Meltdown", sung by Hatsune Miku. The video was able to climb all the way up to No.2 in the Nico Nico Daily charts and was able to receive around 44,000 views in a very short period of time after it was uploaded.
A popular remix of "Meltdown" done by CosMo and illustrated again by Nagimiso.SYS. This version features a different music arrangement as well more expressiveness in Rin's voice, with various voice breaks and changes of pitch.
The PV also features a new design for Rin, looking younger than her original depiction and wearing a lolita dress. This new design resulted in being more popular than her original one. The Hard R.K. mix received its own merchandising and inspired "Meltdown"'s module for Project Diva 2nd. This song is also featured in the EXIT TUNES compilation album EXIT TUNES PRESENTS Vocalolegend feat. 初音ミク
A parody song and a sort of answer song to the KAITO's version of Loli Yuukai. On this versions the roles are swapped and now KAITO is the one sexually harassed by Rin, Miku and Luka. The song was well received, winning a place on the weekly ranking, staying on the top 5 during two weeks (#118, #119).
Rashin Yuukai (Naked Melt)
Shinya-P, luna (illust)
Parody; VOCALOID cover
A parody sung by KAITO with a "S&M twist".
Jashin Yuukai (Evil Melt)
LIQU@. (vocals), Reji (chorus), Windress (mix)
Parody; Human cover
This parody is about "Chunibyo" (中二病: 8th grade syndrome). Simply, one of the most typical symptoms of Chunibyo is that teens often fantasize about themselves as some special or transcendental being.