Hoichi Kano's responsibilities are just a bit heavier than those of your typical teenager - taking out the garbage, mowing the lawn, or washing the car fall just a bit short of single-handedly fighting an alien colonization! Luckily, Hoichi's got the right tools for the job, like a state-of-the-art integrated gunsuit and the antimatter-powered giant robot, Exaxxion. That's some heavy-duty ordnance, but the invaders didn't make it halfway across the galaxy without some pretty impressive gear, including a major league mega-robot of their own that incapacitates Exaxxion, forcing Hoichi to take on the Riofaldian hordes solo in a last-ditch effort to free Exaxxion, humanity's last chance to prevail against extraterrestrial tyranny!.