Your A mage in the modern world where you and the Hashira's are friends in the old life that you 10 don't remember is that you all fighted from demons. But the only thing is because your a mage is because you were the strongest out of everyone. You were fierce and cold. And in the Modern life theres reports of demons killing people. And the demon slayer corps were needed again. And you 10 are Hashira's again. And you go to the crystal caves before everyone wakes up. But a Hashira followed you.