Tanjiro and Nezuko Imitating Eachother
I have a headcannon that Tanjiro and Nezuko share the same braincells. Remember how Tanjiro does the whole "Boom Boom" and "Pow" sound effects? Well I think Nezuko does the same thing. She tries to translate for the others, key word try, but she ends up saying the exact same things Tanjiro is but with different sound effects much to everyone's confusion.