A middle school girl who is introduced as a popsicle vendor at the beach. She feels guilty that her parents were part of the crew of the Premium Anberial. When she and Souta are trapped in a cave, Kurumiko loses hope, but Souta saves her by inviting her to live at the dorm as his younger sister. She becomes the clergy character in Souta's party, and her flag is usually one of story advancement.