Shoujikimono ga Baka wo Miru

Genchi is a young man entrusted the role of raising a young girl named Maruu. She is part of what's known as the "Rooks", special children who are sacrificed for the sake of their country when they turn 16 years of age. These "Rooks" are nothing but an urban legend to most people, but to these two, it is their reality. With a limit on their time together, how can they find what is truly important to them?