Something terrible has happened in the Mushroom Kingdom, 3 strange figures appear from a portal to the Ultiverse wanting power from above, Mario, with the help of Luigi, has to fight to keep them out of their universe and prevent other dimensions from facing the fate that they intend on.
[ SPOILERS BELOW THIS TEXT ]
Luigi is kidnapped by Bowser's Troops, but something else is preparing itself behind the scenes.
Mario and Luigi catch on to what's going on, but it might be too late before the Otherworld achieve their goal.
The Otherworld toy with Mario by sending him to a random game, the only way Mario can leave is by winning.
Mario is sent into another game, but as the players are being unusual, Mario must find a way to escape unintentionally.
With the Flash Door open, the Otherworld prepare an army to overrule the Mushroom World and kill Mario. It's Mario's World against the Otherworld, and the winner keeps their heads.