In Demon Slayer, blood is a motif and a symbol that has both positive and negative connotations and is related to the themes of Perseverance Through Hardship and The Power of Familial Bonds. At several points in the first chapter, Tanjiro repeats the refrain that happiness ends when there is “the smell of blood in the air” (12). In these moments, blood is used to foreshadow violence—specifically, the demon that attacks Tanjiro’s family and the subsequent hardship Tanjiro and Nezuko will face on their quest to turn her human again. Blood thus symbolizes impending danger; it is a demon’s blood that turns Nezuko into a demon herself. It also symbolizes the familial bond between Tanjiro and Nezuko. As siblings, they share a bloodline, and this connection helps them transcend the usual antagonistic relationship between human and demon. As the manga progresses, the reader will learn that Tanjiro and Nezuko’s bloodline is important in another way.

As a recurring motif in the anime, blood splatters are also associated with danger. The frequent, graphic use of blood when demons attack contributes to the dark fantasy of the Demon Slayer world, where demons are an immense danger to humans.