Finding 'Sin' online for free is tricky because it really depends on what version you're looking for. If it's the manga by Shinobu Kaitani, I've seen some fan scanlations floating around on sketchy sites, but I wouldn't recommend them—quality's often poor, and it feels wrong supporting pirated content when creators work so hard. I remember hunting for it last year and stumbling upon a few aggregator sites, but the translations were choppy, like someone ran them through Google Translate twice. If you're patient, checking out used bookstores or digital library apps like Hoopla might be a better bet. Some libraries even carry niche manga, and supporting official releases keeps the industry alive.
That said, if it's the novel 'Sin' by Josephine Hart you're after, Project Gutenberg or Open Library might have older editions since it's a 90s release. But for anything recent or licensed, free options are rare without stepping into gray areas. I’ve lost count of how many times I’ve caved and just bought the Kindle version after fruitless searches—sometimes convenience wins. Either way, diving into forums like Reddit’s r/manga or r/books can sometimes lead to legit free previews or limited-time offers.