Had a friend recommend 'Taken by My Stepfather' a while back, and I ended up scouring the web for it. The title's pretty blunt, so you'd think it'd be everywhere, but it's weirdly scattered. I found the most complete version on a site called Galatea, but honestly, the experience was a mess with ads. I think it started as a serial on an app like Dreame or GoodNovel—those places often have the full, official uploads because they partner with authors. You might have to download their app, which is a hassle, but it's usually the safest bet for getting the whole story without missing chunks. I gave up halfway through because the pacing felt off, but the beginning had that intense, forbidden tension some readers really chase.
A word of warning, though: I stumbled on a bunch of 'free' pdf sites claiming to have it, and they were all either scams, terribly formatted, or just the first few chapters to lure you in. If you're determined, checking the author's name (if you can find it) might lead you to their personal blog or a Patreon page. Sometimes these stories get cleaned up and published on Amazon under a slightly different title later on, too.