Kagamine Rin & Len

Kagamine Rin & Len (鏡音リン・レン), codenamed CV02, are Japanese VOCALOIDs developed and distributed by Crypton Future Media, Inc., and were initially released in December 2007 for the VOCALOID2 engine. They are the second set of vocals for Crypton's Character Vocal Series and are both Character Voice VOCALOIDs. There has since been numerous installments such as additional voice banks dubbed 'Append', an update to the VOCALOID4 engine, and an English vocal.

Their voices are provided by the Japanese voice actress, stage actress, and singer Asami Shimoda (下田麻美 Shimoda Asami).

Concept
The development of the Kagamines began when Crypton formulated the concept of making a pair of female and male voicebanks. The first idea was for two voices of a girl and an identical male of the opposite gender, just like twins.

Crypton originally had the intention of distributing them as twins, but this was not adopted. Crypton stated that they approved of the many different interpretations of Rin and Len's relationship that they saw in different works. Crypton's final announcement was that the Kagamines were neither siblings nor lovers. During their Append's production, Wataru Sasaki (aka. Wat) described them as two bodies with one soul. Wat also said that the Append boxart makes the pair seem like twins, due to the foetal position they were in.

Etymology
When the Kagamines were being recorded in 2007, their names were not yet decided. Their given names of Rin and Len were said to be based on " ri ght" and " le ft" according to Asami Shimoda. She later confirmed in an interview after the Append release that the names were based on Ken and Rin from Hokuto no Ken, derived from a discussion about names that were familiar from her childhood.

Their surname was derived from the developing code combining Kagami (鏡, mirror) and Ne (音, sound).

Their codename of "CV02" means "Character Voice 02".

Appearance
KEI was given a concept by Crypton that included Rin and Len's approximate ages as well as the idea of them being 'mirror images' and, like Hatsune Miku, androids. KEI was not given any further direction as he had already drawn the art for Miku, the first release in the Character Vocal Series.

Rin was the first of the Kagamines to be illustrated and, following Crypton's concept, Len was made to match her. Their leg features were designed to mimic speakers. The keytar Len is often featured holding in merchandise is a YAMAHA KX5. Their main design, of which is most noticeable on their boots, uses the YAMAHA EOS as a design base.

Also, each Kagamine has a particular musical clef symbol associated to their design. Rin has a G-clef (Treble-clef) on her shirt and Len has a F-clef (Bass-clef) on his. In their Append redesigns, they are found on chokers rather than their shirts.

When Rin and Len received a new set of vocals during their Act2 release, KEI took the opportunity to fix flaws in the original artwork.

Kagamine Rin's introduction artwork:
 * Rin has "Act2" on her arm under her "02" tattoo.
 * Rin's top was changed in the introductory image between versions around the armpit area. Frills were added to the bottom of her top in Act2.
 * Her shoulder was not correctly drawn in the original version.
 * All of the yellow bands on her outfit were made bigger on Act2.
 * Her fringe was made thicker above the left eye.
 * In Rin's original artwork, her left knee was thicker and her right leg was too short. KEI corrected this in her Act2 version. Her right leg and left foot positions changed.
 * Forearms were shortened in Act2.
 * The cyber-on-normal clothing design on her detached sleeves was changed from a green bar to a blue one.

Kagamine Len's introduction artwork:
 * He has "Act 2" on his headphones.
 * The cyber-on-normal clothing design on the detached sleeves were changed from a green bar to a blue one.
 * His fringe was reshaped and other strands were adjusted.
 * Len's face, particularly around the cheekbones, was reshaped.
 * His left knee had a minor tweak.

Boxart changes;
 * Kagamine Rin's leg position was changed in the boxart so it was lifted off the ground. The only way the previous position would have worked was if her leg were deformed or broken.
 * Rin's body itself compared to the length of her legs is shorter than in the original boxart, where the legs were longer.
 * Rin's knee is rounded instead of sharp.
 * Both had the cyber details changed on their detached sleeves.

For their appends, Wat wanted them to have a sense of transparency with their design. In clarification to what he meant by this, he stated the "transparency" was in reference to their hearts. Their Append design and the official illustration were made by オサム (osamu).

Continuing the tradition of the Item War Internet Meme, many items were proposed for the pair. In the end, Len's item was a banana because his hair was commented to resemble a bunch of them, while Rin's item was an orange since her bow gave the impression of orange leaves. Before her release, Rin had the road roller assigned to her by accident in a video that suddenly received many views on December 1, 2007. Len had yet to be revealed at the time of the road roller meme.

For the V4x design, Rin was given a more silver/whiter look to make her appearance more refreshing. The design was also based more on the EOS B700 rather than the Kx5 because of its more whiter appearance. In addition, more synthesizer based music symbols were used.

Relations

 * Hatsune Miku; another member of the Character Vocal Series.
 * Megurine Luka; another member of the Character Vocal Series.

Music featuring Kagamine Rin and Len
Examples of usage

Marketing
The Kagamines were marketed as "2 vocals for the price of 1" and were aimed to catch the interest of the growing VOCALOID fandom. Unlike Hatsune Miku, they were not an immediate hit, failing to meet marketing expectations despite receiving the same level of promotion Miku received at the time of their release. After the release of their "Act2" voicebanks, sales picked up steadily and the Kagamines eventually became one of the more heavily marketed VOCALOIDs though have never met the marketing strength Miku gained before them.

Crypton Future Media registered both "Kagamine Rin" and "Kagamine Len" as a trademark on January 29, 2015.

Trivia

 * It took 25 hours (4 hours a day) to record all the Kagamine Appends.
 * Some call Rin and Len by the incorrect names "Lin" and/or "Ren". Though the romanized version of the words could be either, the English version was confirmed as "Rin and Len". Since there is no dubbed version to contend with, the names remain the only official names in existence for the vocals. This is also backed up by the origins of their names as "R" (Rin)" and "L" (Len).
 * Note; "L" and "R" mean "Left and Right". They are the letters you find on a set of headphones (and sometimes other equipment such as speakers). Usually, there is not enough space to write "left" and "right" on headphones. "L" refers to left ear and "R" is right ear.
 * A total of 10 voicebanks makes the Kagamine package the most expansive set of vocals within the VOCALOID2 era. They are currently 3rd in the total number of vocals released behind Miku (with 15 vocals) in second and GUMI (with 17) in first.

Reputation
Google Trends, "Kagamine Rin" and "Kagamine Len"