To be fair it only matters in the beginning and then one part later. Once the reincarnation angle kicks in, it feels a little less Squick. The incest angle starts the plot moving but when the real story shows up, it becomes its own thing and incest angle is largely dropped until the trial scene, by which point the utter battrout crazyness of the rest of the cast will make you wonder why everyone is making a big deal about it. Also Lucifer is an awesome character, as are the four Serephs.