He Joined a Secret Society of Demon Hunters to find a Cure for His Sister

Set in Taisho-era Japan, follows the epic saga of Tanjirou Kamado, a kind-hearted teen who returns home one day to find his entire family slaughtered by invading demons.
Worse, he discovers that his sister, Nezuko, has been transformed into a bloodthirsty demon herself.

Anime Title: Kimetsu no Yaiba