Yumi has enlisted Kanako and Toko as assistants for the Yamayuri Council, but their relationship is strained due to their unfavorable views of each other and the possibility of becoming Yumi's younger sister. As the school year progresses and the council's responsibilities escalate, Yumi feels even more pressure to choose the perfect petite soeur. Can either of them meet Yumi's expectations and be deemed suitable for the role?