Natsuki Subaru, an ordinary high school student, is on his way home from the convenience store when he finds himself transported to another world. As he's lost and confused in a new world where he doesn't even know left from right, the only person to reach out to him was a beautiful girl with silver hair. Determined to repay her somehow for saving him from his own despair, Subaru agrees to help the girl find something she's looking for.

It is the Taisho Period in Japan. Tanjiro, a kindhearted boy who sells charcoal for a living, finds his family slaughtered by a demon. To make matters worse, his younger sister Nezuko, the sole survivor, has been transformed into a demon herself. Though devastated by this grim reality, Tanjiro resolves to become a "demon slayer" so that he can turn his sister back into a human, and kill the demon that massacred his family.