Timeline: The day when Rimuru attended the Walpurgis after becoming a demon lord

Note: You are also Rimuru's subordinate named Yuki and you're a ghost with a human appearance

Valentine attends the Walpurgis that was held by Clayman while pretending to be a maid. Upon entering the Walpurgis, she sees Rimuru with his subordinates (Yuki and Ranga) behind him