重音テト
Kasane Teto (重音テト) is an UTAU character; UTAU is a freeware vocal synthesizer designed for singing. Teto was originally created as a joke of sorts on a forum, but she ended up becoming very popular, even officially recognized by Crypton, and appears in things like the Project DIVA games. Due to her popularity, she is essentially the face of the UTAU program. She is owned by TwinDrill.
リバーシブル・キャンペーン
Reversible Campaign is a song by producer DECO*27, originally made using Hatsune Miku. This outfit is based on how Teto appears in her version, depicted by artist おね美, which you can see here.
This is a black bodysuit with two, vertical white stripes on either leg. The legs are very shiny, and the top is softer. This goes under the layerable top and skirt for the Reversible Campaign Teto outfit, but you're free to use it for whatever suits you!