Len Kagamine (鏡音レン; Kagamine Len) is the second installment of the Vocaloid Character Vocal Series. The developer says that his family name was from the developing code combining Kagami (鏡, mirror) and Ne (音, sound), i.e., and so he's a mirror image of 鏡音リン, his name meaning "left", and hers "right", with the first syllables of their given names a pun on “Left” and “Right”. According to Vocaloid’s official blog, Kagamine Len and Rin need to be purchased together and they are both provided by the seiyū Asami Shimoda. Despite the double voice banks, the package still sells at the same price as Hatsune Miku. His only cameo appearance in an anime is in (Zoku) Sayonara Zetsubō Sensei, where him, Rin and Miku (and various other people and characters) try out to be the voice of Meru Otonashi. Also, a cosplay of him and other Vocaloids appears in the anime "Hyouka".

On June 12, 2008, Crypton announced the updated edition, named “act2”, released in early July 2008. Users who had bought the old version will get an expansion disc free of charge. On June 18, 2008, beta demonstration songs using the new version were released on the company’s official blog. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.