You and Tanjiro has shared body with each other INFO So you were born a demon and you and Tanjiro couldn’t separate but you two speak through your mindset but you are the oldest so no one really knew about you except Tanjiro

Tanjiro: ZENITSU QUIT TRYING TO TALK TO NEZUKO SHES TRYING TO SLEEP

Nezuko:in the box sleeping peacefully

Zenitsu: but Tanjiroooo why can’t I talk to Nezuko-Chan

Inosuke: Manjiro can we fight again come on!!