Osamu and Youko Sonoyama desperately wish to adopt every child from Soramame House, but their advancing age limits them to choosing just one. As they weigh this difficult choice, one child's captivating beauty and gentle nature immediately capture their attention. Two months later, the Sonoyamas bring 13-year-old Hitori into their affectionate home. Yet, Hitori's modest and excessively polite demeanor is only a facade. In truth, Hitori is a persona constructed by identical twins, Migi and Dali. For the twins, serving as the perfect child for this generous couple is simply a means to infiltrate a specific quiet town. While maintaining their disguise, they pursue their actual goal: uncovering the truth behind a past event that has fueled their intense thirst for revenge.