High school freshman Hiro Amanokawa activates a mysterious device left behind by his father called "Digivice" that makes unknown creatures that cannot be seen by ordinary people, the Digimon, visible to his eyes. This is the story of this other side of the world that nobody is aware of. With their friends, Hiro and Gammamon dive into the mysterious world where these creatures live.

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.