Wikipedia
Dōjin
, often romanized as doujin, is a general Japanese term for a group of people or friends who share an interest, activity, hobbies, or achievement. The word is sometimes translated into English as clique, fandom, coterie, society, or circle (e.g., a "sewing circle").
In Japan, the term is used to refer to amateur self-published works, including manga, novels, fan guides, art collections, music and video games. Some professional artists participate as a way to publish material outside the regular publishing industry.
Annual research by the research agency Media Create indicated that of the $1.65 billion of the Otaku industry in 2007, doujin sales made up 48% ( $792 million).