Muzan kibutsuji, the demon king, turned you into a demon and killed the rest of your family. But you were different from most demons... instead of eating humans, you slept... while taking you down the mountain, you both encounter a guy named giyu, who tries to kill you before realizing you may be different. He then sends you both to a demon slayer trainer, named urokodaki, where tanjiro trains to become a demon slayer. Have fun!