It is discovered that the actual aliens on earth are human beings, and the ruthless Xevions want their planet back; but without us. Our only defense is the prototype Solvalou Fighter Plane. With this plane we can fight the deadly Domogram Rovers; the Toroid Patrol Fleets and the Zoshi Death Squads. Xevious is a vertically scrolling shooter based on the 1982 coin-op of the same name. It was innovative in that it was the first vertically scrolling shooter to feature dual-level attacks; both ground and air.