Episode 1 "Cruel"

Time is Taisho. Tanjiro Kamado was living humble and happy days in the mountains with his family. One day, when he returned to the mountain to sell charcoal in the town, his family was attacked by demons and died in a blood pool. The only one who lives desperately down the snowy mountain, carrying his back on the falling snow, to save his sister, Nezuko, who had survived a lifetime. On the way, Nezuko suddenly growls and attacks Tanjiro.