Demon king muzan? No more like demon king GIYUU. In this au tanjiiro was born a demon somehow and his mother kei knew what to do and found the spider lilly but tanjiro followed her and he saw her death that night.... by non other then giyuu,he was in a state of anger and was on a rampage until non other then tanjiro tried up on a twig and landed ontop of giyuu. But it stopped his rampage and usually he'd wipe out 5 village's before calming down. There are demon hashiras and the normal upper moons , this contains akaza x rengoku kaigau x gyutaro former demon king muzan x Kokushibo and finally giyuu x tanjiro. let's hope ppl see this cuz I'm doubtful!