Once upon a time beyond, there lies a world of many islands floating in the never-ending sky above the great world cloud that enshrouds the land beneath them. It is called the Sky World. The islands are enriched with life of many sorts, nourishing with environments hot or cold just like the different parts of our earth. People made most of the islands their home, living and coexisting in a time of peace and prosperity with the help of a mysterious ancient technology that helped unify them slowly and steadily. The ancient technology is known as 'Unity Technology' - 'Uni-Tech' for short.

No one knows where it comes from or when it was first created, only that it holds the key to answering all problems with hunger, conflict and many more. It also has the power to restore the damaged environments of nature and fill them with life once more. That is how the world came to be. But like two sides of a coin, where there are powers meant for good, there must always be powers made from evil.

A malevolent darkness, creatures of negativity and destruction. The creatures known as Shadows set their sights on the people of Sky World and all their creations. Their only desire is to ravage the islands until they are wastelands consumed by death. In the first few clashes, the people were overwhelmed by the Shadows' powers and came close to extinction.

But when hope was almost lost, a few souls of pure nobility unlocked a special ability powerful enough to light the path throughout the dark times, and in time, the special type of people of Sky World awakened their special powers with goodwill and purity in their hearts. The powers are known as Omni skills. Wielding their newfound powers, those heroes vanquished the Shadows time and time again, protecting the innocent and their futures. These heroes became the first generation of what people call the Sky Guardians.

Throughout centuries and generations, these Sky Guardians of pure heart have expanded and done it all: they fought against masters of evil, defeated tyrant and corrupted rulers of the old kingdoms, saved more lives in dangerous situations and gave hope to the hopeless. Under their steadfast protection, the lands recovered and civilisations united. And today, a new generation of Sky Guardians will step up and pave the way for the people to march into the future.

And it all starts with the academy of all heroes: Sky-Hi Academy.