One day everything changed, an alien civilization of immense power sent a probe to the Earth. Their forces were so powerful and overwhelming the combined might of the UN forces were destroyed in an eyeblink. But after the initial battle the aliens settled into a quietly peaceful, even polite observation of the citizens of earth. Life went on as usual except for the odd appearence of a robotic probe. People accepted their new neighbours.
Everyone except a small group of students at a local highschool. Drawing upon long since forgotten knowledge, the Magic User's Club sets their mission as the defeat of the forces of the alien "Bell".