The world of Smash has always been a mystery to all, to live freely and interact with others. However, things begin to go awry, causing everyone to be sent inside the deep depths of the world of Smash and forget their past friends. Little Mac, Shulk, Lucario, and R.O.B. must force themselves to work together in order to find the truth behind the new world of Smash.

While visiting Princess Peach one day, Mario is transported to a new world that looks exactly like the Mushroom Kingdom, but something doesn't feel right. Mario feels as though there are dangers awaiting him in the future. Taking place during Adventure Mode in Melee.