Princess Maker 4 Portable

A war between humans and the race they call demons has been grinding on for years. A human soldier named Isabelle manages to bring it to an end — and then disappears. The protagonist, a soldier who knew her, spends ten years searching for her. When the war begins to ignite again and he finally finds Isabelle, she has almost no time before vanishing a second time — only enough to pass him a young girl and a demon servant named Cube, and to leave him with the understanding that the child's future and the fate of both kingdoms are now in his hands.