I read a lot of fanfiction in general, so I know of major sites for fanworks that I frequent:
- archiveofourown.org
- fanfiction.net
The background for this question is I wrote the beginning of a fanfic based on the VN Pale Spectrum, but I haven't really found any sort of community online where the fanfic might be appreciated by other people that like this game.
At the moment, I'm planning to post it on archiveofourown.org (in a few weeks, once I get "invited" to the site) because fanfiction.net, despite the wealth of content there, is a bit of a pain in the posterior.