FANZA
FANZA is a site dealing with adult content in general. It is separated from the all-ages version DMM.com by domain name, and FANZA is "dmm.co.jp".
It also distributes adult videos (video distribution and packages), adult e-books, R-18 doujin games, doujin comics, doujin photo collections, doujin videos, etc. It also offers adult auctions, and product samples of comics and CG collections are posted on pixiv. It also offers adult games on FANZAGAMES.
Many doujinshi works are mail-ordered and distributed through other sites such as DLsite, but original works are also distributed. Although the current situation is limited to live-action works, there are some cases in which works that are acceptable on DLsite are not listed as "NG" (no go) on FANZA (because even works by major makers are rejected by FANZA as NG, it does not mean that they are rejected because they are doujinshi).
On pixiv, illustrations are posted as commercial drawings of browser games, a sample of which is mentioned above. Caption search and other search methods are comparatively easier to find than tag search. this tag would also be useful for negative search of R-18 series works on DMM.com works.
In March 2018, the site was taken over by Digital Commerce, which was separated and spun off from DMM.com, and on August 1, the site name was changed from DMM.R18 to FANZA.
