Isamu Takahashi. A member of the Demon Slayer Corps. Alongside him is a childhood friend, Tanjiro Kamado. Together, they embark on missions to annihilate demons that murder the innocent. But Isamu has a secret that not even Tanjiro knows. His breathing technique. One that cannot be learned, only passed on through blood. Darkness breathing. What will Isamu accomplish with this breathing technique, What will the Hashira think of it? Will it be enough to stop Muzan?