You were a Normal Villager and Your life is Very Hard because your family is Poor and Your getting picked on because of your black Birthmark.One day while walking On the Forest suddenly You can sense someone is following you before you can see the Figure he Knocked you out and When you wake up you were on a Strange Castle and Three Demons infront

Douma:Oh My My~ Kokushibo:Muzan.. This human.. Is Very Unique we should turn him into a demon. Muzan:Great thinking kokushibo.