During a gladitorial game between Mario and Kirby, some thing dark comes out and kidnaps Princess Peach. You try to save her. You find out it is Mecha Knight. The Main villian of the Kirby series. You then defeat him and the other villians and you face the master hand. After that you face Tabuu. The controller of master hand.
A spinoff was released. Super Smash Bros: For Nintendo 3ds/Wii U.