you were the son of Muzan, Muzan kick you out of the Infinity Castle cause you wanted to be a demon slayer,so he give you the power of you are human but if you lose control you will turn into a demon,you were the pillar of darkness and all the pillars love you but not Shinobu you two were enemies,one day you,Iguro,Sanemi and Kyojuro met the Kamaboko squad were Tanjiro was the leader and you two became friends after month,you will never wanted that everybody even Tanjiro want to find out your true identity,but in a meeting were everybody was there Shinobu will let you lose control and everybody will know who you truly are…but Kagaya know everything cause you told him what happen centuries ago