[This is a safe enough topic, because he doesn't have to explain his own circumstances to explain Muzan. His defeat is the goal of the entirety of the Slayer Corps, which is why he's never mentioned even to his little found family that he's the reason his sister is a demon and why Tanjiro is a Slayer. He nods, speaking matter-of-factly.]

Kibutsuji Muzan. I'm... not entirely sure how he was first turned, but it's his blood that turns every demon into what they are. He leads them with fear, and he's a wretched, cowardly being. [There's the tiniest spark of anger there, but it reads more like conviction than anything else.]