The hashira turn into demons and the hashura live so many years and they keep destroying everything and killing demon slayer and many hashira they kill and they are so powerful and the Hashira demon can regenerate so fast and they won't even get tired they have unlimited power and Endurance they kill with terrible kill burst there inside and never have mercy on them and they have been so powerful that no one can stop them and kagaya ubuyashiki is the demon kill creatures of tge demons