The story starts in a future world where hope still survives. The year is 3716 and an alien threat known by the name “GIGANT” has forced the human race to leave the Earth behind. It is now a wasteland, and the people live in huge, flying cities. One of them, called ARK-3, is your home. A mysterious girl named Ciel is found and brought into your care. It will be up to you to raise her to adulthood. The management gameplay gives you a helpful schedule to plot activities. These include things like spending time with her, hanging out with friends, hobbies, classes, and finding a part-time job. Your choices will decide the type of person she becomes and how the story ends.