The term first appeared in the Meiji Era, where literature "Doujinshi" had already appear during that time. Initially these circles gathered around to share their works on Tanka, Senryuu, East Asian Calligraphy, and Art. At that time, these people who create them are mainly Waka writers.
One famous example is Ozaki Koyo, who led the Kenyusha society of literary writers that first published collected works in magazine form in 1885.
Doujin nowadays have shifted from mainly literary works to manga and anime works, although groups that write literary doujin works are still available. With the expansion of manga and anime culture, many of the doujin available today are mainly derivative works. Manga artists including Shotaro Ishinomori and Fujiko Fujio that formed New Manga Party (新漫画党, Shin Manga-to) contributed the expansion of content creation through doujinshi. As they make their profession debut, some who got inspired by their works then followed in their foot steps.
Then, on 1975, Yoshihiro Yonezawa and a circle of friends, including Teruo Harada and Jun Aniwa became dissatisfied with the strictness found in Nihon SF Taikai, the annual science fiction convention in Japan. They also wished to study manga and explored the potential, as commercial works became unchallenging and mainstream. Hence they founded Comic Market (also known as Comiket). The rest is history.
Doujin of Today
As mentioned above, Doujins of today are mainly derivative works from anime and manga. With the contents often being a parody or fan stories. There are also many works that are mainly for adults, and has contents that are highly sexual in nature. While these works may be created from scratch by each respective creators, they are however not original, hence highly susceptible to copyright infringement.
Although doujin is usually referred by many as a form derivative expression, there are also works that are created entirely from the scratch of concept, and did not borrow any elements from an existing work. These kind of works are considered as original works. Touhou Project is the best example of this category.
One thing to note is that the word "doujin" simply refers to "Companion", although it is tied closely to derivative creation.
The word "Doujin" itself originally means to "Group", "A gathering of people with the same interest that forms a group". With the advancement of internet or printing technology, the meaning starts to derive from the original, creating various misunderstandings where people misunderstood doujin as something of a "show works to each other within the circle of friends" concept.
In doujin, there are various genres that can be created from a specific arwork: Adults Only, For Male, For Female・GL・BL・Yaoi and many more. These are the common genres found within the doujin market.
While it is generally known that most doujin contents are purely sexual (Adults Only, Yaoi, Yuri), there are all ages doujin as well, and most of the them are original. The same goes to the quality of the doujins - most of them are self-produced and may vary in quality, especially the art.
It is common to think or label a person a "doujinka" the moment they start on derivative creation. Since the works are not available commercially.
Generally, doujin and official, commercial products are antithesis of each other. Doujin products are often not available in a large, wide scale for most people to purchase as they are produced mainly without the permission from the original author/artist. It is however agreed that doujin encourage people to create something and show their creativity and talent, which is shown where groups like CLAMP and TYPE-MOON were once doujin group before they went commercial.
However, due to copyright issues, doujin are often being labelled as illegal creations by the law because they are created without the consent from the original artists. With more people getting involved in doujin creation, along with the fact that doujin are mainly self produced (with both original and derivative, and some even a mix of both), the authorities allowed for the doujin scene to actually grow, which in return create many talents actually started underground and climb themselves to the commercial world. Many companies from the anime and manga industry took that approach in order to raise talents from the underground scene. This approach gradually reached global as well, with artists like VOFAN entering the industry as well (though not from the doujin scene).
Similarly, while doujin is commonly said to be completely unrelated to commercial goods, there are professional doujin authors and artists in the industry, which they do both commercial works while participating in creating doujin works at the same time. However, they are met with the following restrictions :
- Due to copyright reasons, along with other restrictions set by the company they worked for, some artists are not allowed to create unofficial (derivative) works that they were involved in. This continues even after they no longer work with the company, as they are bounded by the contract sign between both parties.
- Most companies forbid artists to create hentai works of their own works as well. Especially when the said work is actually all age. Doing so may cause the company to fire the artist under the reason of breaching the rules (company or contract).
- They are not allowed to produce doujin that contain any artworks not found nor included in the original, commercial version of the product without given permission from the company responsible. Fortunately, companies that forbid them from releasing it are usually rare.
With that said, these professional artists usually release sketches, works and unofficial but extremely rare artworks of a commercial work (especially famous, special limited edition goods) that are not available commercially in the market.