What was doujin? What did doujin mean?

Doujinshi refers to different works created by the same author or the same work, usually modified or created to achieve different storylines or characters. Doujinshi would usually modify the original storyline or character to create a new work. These works may have the same theme or storyline but present different characters and story atmosphere. Doujinshi works could be novels, comics, animations, games, and other forms of work. They could also be the same author or different versions of the same work. Doujinshi works could stimulate creative inspiration and enrich people's imagination, but they also needed to pay attention to respecting the copyright of the original work and the rights of the author.