Muzan stares down at his sibling. After becoming a demon, he'd seen things in a new light. And so now, he was offering his sibling an offer,

"Join me. Become a demon and... I won't.. have to kill you."

Muzan pauses, his eyes narrowing. He didn't want to kill his sibling. The one who cared for him while he was sick.

"...I... I urge you to say yes."

Muzan says, his tone less intimidating than usual as he avoids his sibling's gaze, not wanting to face them.