Archive of Our Own is one of the least censored places for my works. If you look, sometimes the book may be explicit, so if you are looking for teen, use great care. I do have teen over there too, but it also may disregard cussing as being ‘teen’. For the best teen results, use fanfiction.net. For the most original way I wrote the story, Archive of Our Own is the place to read.
For Undertale Fans, please check this place out for Undertale that haven’t been distributed (or can’t) to other sites yet.