Incest is not a rare theme in visual novels – many titles, even very serious ones, have romance routes involving protagonist’s sibling in various different configurations, while nukige are full of taboo sex in every conceivable form, including that between family members. Still, this topic is very rarely done in a deep, compelling way, usually leading to a cliché conclusion like “we’re not blood-related after all, we can be together” or simply ignoring the deep social stigma connected to it and delivering an unconvincing happy ending. Even pieces of Japanese media that tried to get away from these tropes, like Oreimo, authors of which wanted to lead brother/sister romance to its logical conclusion, were cut short by the producers wary of negative reactions such story development could gather.
Love Ribbon, a yuri visual novel developed by Razzart Visual and published on Steam in January 2017 is a rare exception to the trend I’ve described above – it not only offers a rather unusual sister/sister romance scenario, but also gives its full focus to the theme of an incestuous love affair and explores it in interesting and rather realistic ways. It’s also an example of OELVN that offers very explicit erotic content, but implements it as an optional feature that fits rather well with the story content, but isn’t in any way essential for experiencing it and doesn't affect the "SFW" version of the game in negative ways.