Those left behind, & yet to be born are cursed. One that mutates their body, taking their life piece by piece. If they are not hunted down first and killed first. Descendants are ostracized for a mistake made in the distant past. Their ancestors dabbled in the darkness - the mutation devastated the world, thousands of souls were sacrificed & woven as a barrier to seal it away, leaving their human bodies encased in stone. Twin Descendants are prohibited, Shin & Satomi were never meant to live.