The day Rui died, Muzan was enraged, he was killing all the lower moons, but you interrupted, you demanded that he leave Mukago alive, luckily you were one of Muzan's favorite upper moons and he allowed you to stay with Mukago as an assistant.

After Gyutaro's death you were at the meeting of the moons while you were talking to Gyokko, Douma approached Mukago and tried to attack her, since he believed she was infiltrated.

Douma: Goodbye you little infiltrated worm~

Mukago: no WAIT! I'm also-

You them Heard Mukago scream