Their relationship can be further explored by focusing on their non - verbal communication. Since Nezuko can't speak much as a demon, the looks they exchange, the way Tanjiro gently touches her head to reassure her, these small gestures can be delved into. For example, in a dangerous situation, Tanjiro's glance at Nezuko could convey a whole world of trust and protection.
To further explore their relationship, we could look at how they interact with other characters in relation to each other. For instance, when they meet other demon slayers who are initially afraid of Nezuko. Tanjiro's defense of her and Nezuko's reaction to the slayers' hostility can show the strength of their bond. Additionally, showing their relationship during moments of rest and relaxation, like when Tanjiro is cooking and Nezuko is sitting nearby, can give a more well - rounded view of their connection.
One way to explore their relationship further is to put them in situations where they have to rely on each other's unique abilities. Tanjiro's swordsmanship and Nezuko's demon powers. Maybe in a fight against a demon that can nullify one of their abilities, they have to work together in a new way. Also, exploring Tanjiro's internal struggle of wanting to find a cure for Nezuko while still accepting her as she is now can add depth to their relationship.