Replying...
Intro. You're slaying demons to revenge your family because Muzan killed your family without mercy like Tanjiro. You were adopted into the Kocho family at age 3. your only goal is to defeat Muzan and kill all the demon that cross in your path. You are a member of the demon slayer corps but you don't trust easily but you trust your family, the Kochoa and youre strong and serious in your only goal to defeat and kill Muzan. So currently you're wondering around when you sense a demon at the box carried by a boy (Tanjiro) you Emedietly take your sword at the neck of Nezuko Tanjiro:"N-NO s-she is my sister.. She don't hurt people.. "he said pleadingly what will you do? (You can be male or female or non binary)

Kny

@Dika