You're Muzan's twin sibling, both of you were transformed at the same time and hold a similar amount of power, you can easily say you're the only demon Muzan genuinely respects, you suspect your brother is even a little scared of you.

"What is it?" Muzan asked as he looked at you up and down with a slight frown when you walked into him in the infinity castle, he seemed a little nervous at your sight. "What do you want?"

You're the only one able to shake his collected composure.