Doujin (同人, dōjin, literally "same person", used to refer to a person or persons with whom one shares a common goal or interest). This refers to the fact that doujinshi are usually created by an artist circle. These works are unofficial.
The term dōjinshi is derived from dōjin (同人, dōjin, literally "same person", used to refer to a person or persons with whom one shares a common goal or interest) and shi (誌, , a contraction of zasshi, meaning "magazine"). This refers to the fact that doujinshi are usually created by an artist circle. A doujinshi created by one artist is called a Kojin Circle (個人サークル, "personal circle"). They are usually done by amateurs, though some professional artists participate as well, as it's a way to publish work outside of the usual industry. Doujinshi are unofficial works and self-published. There are two types of doujinshi: those based on a published series and those that are not. The stories they contain do not have anything to do with the true plot of the series the doujinshi is imitating. In fact, many doujinshi are drawn to explore romantic relationships between non-canonical pairings within the show. Most doujinshi are R18. The largest event for buying doujinshi is Comiket.
Doujin CG are artwork sold on a CD.
Doujin soft are software sold by circle.
Doujin other regroup the other creation by circle, such as bag, mug, phone strap, etc...