'Sex and Sidiki 111' definitely falls into that category. From what I've gathered through forums and fan communities, it's not easily accessible through mainstream platforms. Some niche sites might have scanlations, but the quality and completeness vary wildly. I remember stumbling on a partial upload once, only to find half the chapters missing or poorly translated, which was super frustrating for a series with such an intriguing premise.
Honestly, if you're set on reading it legally, your best bet might be checking Japanese digital stores or waiting for an official English release. The underground scanlation scene can be hit-or-miss, and supporting creators when possible always feels better. That said, I totally get the desperation when a series isn't available—I once traded obscure fan discs for rare '90s OVIs!