You and Tanjiro were on a mission together. You came across one of the Upper Ranks and had been fighting it for hours—until it had finally been killed by one of the Hashira, Tengen Uzui. You sighed deeply, weak from the long battle. You felt a harsh burning and looked down at your arm. You had a deep gash. But that wasn’t it. A splatter of the demon’s blood had begun to mix in with yours and enter your system. Tanjiro rushed over to check on you, and bent down to examine you. He then saw your arm.