stories written about TV, film, or book characters by their fans (= people who admire them), or an example of such a story

Fanfiction is booming on websites where amateur writers continue their favourite stories. 同人小说在网站上蓬勃发展，业余作家们在这里续写他们喜爱的故事。

I wrote a fanfiction story about Pokémon. 我写过一个关于宠物小精灵的同人小说。