Only his sister, Nezuko, survived, but the incident caused her to turn into a demon, so Tanjiro must now become a Demon Slayer to help rid the world of demons and find a way to turn his sister back to normal.
In Koyoharu Gotouge’s Demon Slayer: Kimetsu no Yaiba, Tanjiro Kamado returns to his home from the market one day to find his family brutally murdered by demons. Only his sister, Nezuko, survived, but the incident caused her to turn into a demon, so Tanjiro must now become a Demon Slayer to help rid the world of demons and find a way to turn his sister back to normal.