The human kingdom is at war with the kingdom of magical creatures, commonly known as "demons". Human heroine Isabelle puts a stop to war, but disappears. Protagonist, a human soldier, sets out to search for her. 10 years later, when the war between humans and demons is igniting again, he finds her, only for her to pass a little girl into his care, along with a demon servant Cube, and disappear again. The fate of the girl is now in protagonist's hands. And with it - the fate of both kingdoms.