The protagonist, Haruna Iba, is a university student in Kitakyushu. One evening, she visits the general hospital where her brother works. Her brother, Masato, a surgeon, had just finished operating on an emergency patient when he said something strange to her: "The locket pendant the patient had contains a photo of me as a child. Why is that?" Soon after, they learn an unexpected truth from their parents—the woman who had been brought in, Yumiko Sakurai, is Masato's biological mother. As their f...