Yes. If you try to publish the fiction, as in to make money, you will be sued. Some authors also dislike fanfiction and will sue you if they find the fiction online. Find out before you post anything...
It's not known when or where fan fiction (also called fanfiction or fanfic) was created, although derivative works based off of those already published have been around since the 17th century,...
Here are some links: narutofic.org/ mediaminer.org/fanfic/src.php/a/Naruto www.narutocentral.com/features/fan-fiction/ mangahelpers.com/forums/showthread.php?t=2998 and...