Try archiveofourown dot org. It allows literally anything as long as you tag it with some basic content warnings so other people can search for it and don't have to end up reading about, idk, shitting on someone's exposed internal organs, if they don't want to. It's supposed to be for fanfiction, but it does have an original work category, and if you're still worried you can name your main characters after anime characters (so long as it's not something obviously contradicting the setting, or if you tag it "Modern AU" or "Mundane AU").
You have to choose a rating for the work and warn for any "Underage," "Graphic Depictions of Violence," "Rape/Non-Con," and "Major Character Death," or "Choose Not to Warn," but there is no judgement from the site admins for using any of these tags, and you can choose to moderate comments if another user is being rude to you for it (which is very rare). It's also a really good idea to tag for other common squicks like scat, vomit, etc, so that people who don't like it don't have to see it and so people who do like it can actually find and read it, but it's not actually required. You do have to get an account, but you can use a throwaway yahoo email (lbr, you probably have one for pixiv or exhentai already), but turnaround for new account requests is pretty quick, and it means you can edit or add to your own stories at any time and bookmark your favorites.
If you've heard that AO3 is full of tumblr SJWs--it does tend to lean a bit liberal, but it doesn't get the sort of "I'm pretending I'm so good but I actually just want an excuse to be mean to people in ways that really aren't liberal at all" jerks that tumblr does. Most of the authors I know on AO3 are very good people who basically believe in not being dicks to people (except fictional ones), and the entire premise behind the site is freedom of expression for the most obscene fictional material possible. The only things that would get you taken down are posting spam, RL CP (for obvious reasons), repeatedly omitting the ratings or major content warnings (which, again, aren't censoring the work, they're for organizational purposes so the site search actually works), or actually harassing people (leaving lots of mean comments, being extremely racist or homophobic to a user personally [why would you even do that? if you're on this site, why are you judging anyone else], ignoring requests to go away, going after their friends or other people who commentedPost too long. Click here to view the full text.