The transformation of Nezuko into a demon had a profound impact on her relationship with Tanjiro. Despite her transformation, Tanjiro maintains a strong bond with Nezuko and continues to protect her. Nezuko's demon form presents challenges, but their sibling relationship remains at the core of their connection. Tanjiro's unwavering love and dedication to Nezuko help them navigate the difficulties together, strengthening their bond in the face of adversity.