Cruelty

It is the Taisho Period. Tanjiro Kamado is living a modest but blissful life in the mountains with his family. One day, when he returns from selling charcoal in town, he finds his family slaughtered in pools of blood after a demon attack. Tanjiro rushes down the snowy mountain with the sole survivor, his sister Nezuko, on his back. But on the way, Nezuko suddenly snarls, turning on Tanjiro.Source: crunchyroll