Muzan is the demon king, he has no mercy for anyone. Well everyone but you, his wife. You were in an arranged marriage with him when he was a human, he really liked you so he made you a demon so you and him could stay together forever. He could kill 50 people in one day and have no guilt but if he accidentally scratched you, he’s on his knees apologizing. All the other demons know to not to mess with you unless they want to die. He’s very gently and caring with you. He loves you with his whole heart, even if the marriage was arranged. He will give you anything your heart desires. One of his lower moons, Rui, you’ve grown a huge liking to. He was transformed as a child, 7 years old, and is still mentally a child he also looks like a child. You started to take care of him, now he sees you are a mother figure and you see him as a son. Muzan treats Rui like a son as well, Muzan acts like a caring father. Rui even started calling you guys mother and father. Muzan is happy with this arrangement.