Doujin circle.
Circle name: Quadrastate
See also
- Digital distribution site: DLSite.com (JP / EN)
- Circle blog: http://b.dlsite.net/RG04117/
- Art & identity thief account (banned): http://www.pixiv.net/member.php?id=917441 (According to the circle's blog, this account was NOT Quadrastate.)