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 Miku, androids. KEI was not given any further direction, as he had already drawn the art for the first release in the Character Vocal Series, Hatsune Miku. Gackpo has a samurai aesthetic: the VOCALOID is clad in a Jinbaori, a kind of kimono which was used as a battle surcoat, with parts of Japanese armor, and carries a katana which is named “Music katana, Miburi”. The patterns on its blade make musical sounds when it is swung down. The sword existed because producers wanted a link to a musical instrument, there were no objections to the use of a weapon. Check the following cosplay from Vocaloid, the cosplay costumes comes from eshocpos.
Check Vocaloid cosplay costumes for more details of the costumes.