Ten years after the collapse of the Subspace Emissary a new world was born from a resulting unknown blast wave. This new world, composed of notable places such as the Mushroom Kingdom, Hyrule, Sector X, Zebes, and many others, is known only as Li. Characters from all walks of life are forced to work together on this planet in order to survive, cause you see... there is one major problem filling this world with distraught: a disease known as Starvia.
Before anyone could even begin to know the wonders of Li the disease spread like wildfire, turning characters from all backgrounds and abilities into infected beings all glowing with the familiar black-purple aura that the Subspace foes once possessed. Groups of the tainted characters gathered in the west presumably in search of the diminished essence of Tabuu; and the origin of the explosion. Once they find this origin of essence they hope to destroy Li and all those opposing them, then set off to create their own space of darkness to dwell in.
The brave souls that are still healthy slowly begin to understand exactly what's at stake. The courageous warriors of the Smash Brothers universe must band together in finding this point of extraction and destroying whatever essence of Tabuu is left to save Li from this taint.
Leaders in battle, Mario and Sonic both have very different views on what they should do to end this plague and both heroes have been arguing about their decisions for months now. Mario wishes to recruit all the brothers and sisters of the smash universe to push towards the point of essence and battle their way to victory just like they did on Subspace, but Sonic wishes to create a massive bomb to destroy the planet and flee to find a new planet.
Without a majority vote on how the Life Sphere wants to proceed Sonic and Mario are stuck wondering what to do. Now it is up to the newcomers and all the other brave souls willing to step up to the plate to choose who's side to take, be it Mario, Sonic, or their own method.
It's time for a stand. But could Tabuu still be alive? Does Master Hand and Crazy Hand still lurk to wreak havoc on the characters of our time? How much longer does the planet have before the Starvia overcomes the Life Sphere? Only the mysteries of life itself can solve those questions.