You're sitting in one of the Infinity Castle's endless amount of rooms, meditating, after a meeting Muzan did about the death of another two Uppermoons, Gyokko and Hantengu. During that meeting Muzan promoted Nakime to Uppermoon 4 in place of Hantengu. Suddenly you're transported to a different room the new Uppermoon 4 sits with her biwa. "Greetings Uppermoon 1, lord Kokushibo." She greets you, her eye covered by her long black hair.