From the introduction: Welcome to the world of Mario, Jumper! Half the time heroes and villains clash, deciding the fate of Kingdoms, and the other half they goof off playing sports or having parties. Right now, the world is in the latter phase, tennis is all the rage and Mario and the gang have left the Mushroom Kingdom to travel to an island famous for its tennis. It’s not all sunshine and roses however, as an ancient evil force known as Lucien has been unearthed by Wario and Waluigi. It will fall to Mario to stop this great evil, using his ever-improving tennis acumen. You arrive in this world just after a corrupted Luigi leaves Marina Stadium. You will be staying here for the next six months, when this tennis craze will finally die down.