Based on the anime Creamy Mami, the Magic Angel. The original tells the story of a 10-year-old girl named Yuu Morisawa, who gains a magical ability to transform into a grown-up young woman, eventually becoming a pop star and acquainting the inhabitants of the Earth with the rest of the galaxy. Yuu appears in the game, but is not the protagonist; the player controls four young women in four different scenarios: two of them, Yuri and Aya, on the Earth, and the other two, Ora and Sita, in an alien world, mixture of sci-fi and medieval fantasy. The story goes beyond the original anime by introducing a magical, sacred land known as Finality, populated by fantasy being, and calling the guardians (the four girl protagonist) to bring peace to the galaxy.

Futatsu no Sekai plays automatically for the most part, except key scenes which allow interaction - two, sometimes more choices that have to be done by the player. In many cases these choices are merely cosmetic, or may lead to a different text description and scene.