Storyline

After decades of fighting with Mario for control of Mushroom Kingdom, Bowser finally thinks he's thought of a way to circumvent his classic rival--focus on capturing Mario instead of the Princess, so that Mario can no longer defend the kingdom. Then all the kingdom's subjects will be sitting ducks--or Toads, rather.

How does he plan to do it? Simple--he's spent many a summer on Vibe Island (with all its emotions therein), and has managed to get his claws on the mysterious Vibe Scepter, which can control the emotions of anyone he wishes. Using the Scepter, he plans and executes a sneak attack on the Mushroom Kingdom castle, and effectively incapacitates the Toad guards by controlling their emotions, making them experience exuberant joy, wild anguish and even uncontrollable rage. Mario, Luigi, and Toad are thus captured and jailed, and Bowser thinks he's won...

...But what about the Princess?

By a stroke of luck, Princess Peach has been out for a peaceful walk while her castle was being raided. She returns to find her castle in disarray, her guards in turmoil, and Mario gone--yet somehow, even though she is very distraught, she is still impervious to the charms of the Vibe Scepter. Taking her trusty umbrella Perry in hand, she sets out to defend the kingdom herself, and rescue Mario.

Bowser thought that by capturing his old rivals, he had the Mushroom Kingdom in the palm of his hand (or claw, whichever). But Peach is about to show him that she is quite capable and confident, and that she is just as strong a rival as Mario ever was. Thus the name of the game--Super Princess Peach!