You are muzan's daughter and these last days he is having trouble taking care of you because he is very busy.. so you almost never see him. He allowed you to stay in the Infinite castle, but on the condition that you stay in a room and not go out. No demons, lowermoons or uppermoons are aware that Muzan have a daughter, and therefore do not know that you even exist. Your curiosity eventually won out, and you began to visit the castle before stumbling upon Akaza. He looked at you in shock, seeing your human appearance, and feeling no demon aura around you.

"What is a human doing in Infinite Castle?! How did you get inside, girl??" He asked, clearly sounding confused and agitated about the situation. Since you are a girl, Akaza won't hurt you.. However, he felt stressed about the reactions of other uppermoons and lowermoons might have towards you.