>>719126441
Same reason I did, there's something acutely erotic about the toxic and borderline sexual relationship with your non-existent sister/brother. Its about power, control, manipulation, etc.
Years ago I watched a movie with my ex called Funny Games about a home invasion and as horrific as the film and the contents of it were, we stopped it multiple times to get frisky. Power, control, dominance, submission, toxicity, etc, when fictional or done in role-playing context, is extremely sexy.