A fan disc is an expanded-content game disc, usually released by a game company after the game's first successful launch. The content adds new images, music, minigames, character information, demos, etc. It usually extends the game's time line by adding in a new shorter game; however, they are not considered true sequel

Sequel

A sequel is a narrative, documental, or other work of literature, film, theatre, or music that continues the story of or expands upon issues presented in some previous work...

s. The creation of a fan disc usually signals the end of a series.

Eroge

Eroge

An or Ero-ga is a Japanese video or computer game that features erotic content, usually in the form of anime-style artwork. Eroge originated from galge, but unlike galge, they feature erotic/pornographic content.-History:...

 visual novels such as Popotan

Popotan

is a Japanese adult visual novel developed by Petit Ferret with character designs by Akio Watanabe under the alias Poyoyon Rock. It was originally released as a PC game for CD-ROM on December 13, 2002 and subsequently re-released on DVD-ROM and for the PlayStation 2 with certain scenes removed...

are good examples of games that usually get fan discs. Sometimes a fan disc is made as a compilation of the two separate, but similar games to link them (the Come See Me Tonight

Come See Me Tonight

is a visual novel developed by Sekilala about a boy whose parents took off after leaving him ten thousand dollars and with no home. His aunt Chidori took him in and told him to choose one of her girls to marry...

series is an example).

These extensions are generally not translated. There are only a few fan-translated attempts, such as Tsukihime's

Tsukihime

is a Japanese eroge dōjin visual novel game created by Type-Moon, who first released it at the Winter Comiket in December 2000. It was adapted in 2003 into an anime series, Shingetsutan Tsukihime, produced by J.C.Staff and Geneon, and a manga series, which has been serialized since 2004 in...

PLUS-disc translation by mirror moon. Recently, MangaGamer released the first official translation of a fan disc, said title being the Edelweiss fan disc, Edelweiss Eiden Fantasia.