Osamu and Youko Sonoyama want more than anything to adopt every child from Soramame House, but the wealthy couple can only pick one due to their increasingly old age. While they contemplate this delicate decision, one child's alluring beauty and gentle soul instantly draw them in. Two months later, the Sonoyamas welcome 13-year-old Hitori into their warm and loving home. However, Hitori's humble and overly polite exterior is merely a masquerade. In reality, Hitori is a carefully crafted character played by identical twins Migi and Dali. For them, being the ideal child of this kind couple is merely a stepping stone to infiltrating a certain quiet town. While dutifully protecting their cover, the twins work toward their true objective: to discover the truth behind a past incident that left them with a burning desire for vengeance. The stork brought an angel into the lives of a childless middle-aged couple. His parents are kind, their house is luxurious and the meals are delicious, but to continue to revel in this happiness Hitori must conceal a certain fact from his family...