Everything in the world is far more complicated than it seems. Objects go beyond matter, time cannot truly be measured in a formula, and every season has an essence. Once you understand, it's simple, really. All four seasons - Spring, Summer, Autumn, and Winter - have a soul. That soul is called Essence - an embodiment of a season. When an Essence is healthy, its respective season is in perfectly normal condition. But when an Essence is weak, its respective season goes completely out of whack. When this happens, it is what scientists call a natural phenomenon.

However, when an Essence is consistently weak, it needs a new, strong host. Originally, the Essences had no hosts - they never needed them. But as 2017 approached, all four Essences were growing progressively weaker; if they became any fainter than they already were, Earth would enter an age of havoc.

So by following their primal instincts, the Essences searched for a host. It's incredibly difficult to access a host - they must be physically weak or on the brink of death for the Essence to connect with them. An average, healthy human is far too strong for an Essence to invade their body. But these circumstances present a problem; when an Essence enters their new host, their host is in an extremely weak state - it's difficult to tell if they will even survive for more than a week.

But after constant searching, the Essences found four hosts perfect for their cause. They were all on the brink of death, yet, they were strong enough in their own way to withstand the infecting taint of an Essence occupying their body. These hosts managed to connect with their respective Essence - like two puzzle pieces never meant to be taken apart again. These humans recuperated, and while they didn't combine with their Essence, these new hosts gradually came to truly embody the seasons.

Our four humans aren't immortal, nor are they invincible. And the world definitely won't go any easier on them just because of their Essences.

It's like introducing new, foreign tissue to someone's body; you can't just expect your immune system to accept it automatically. Usually, in this case, you have to keep your immune system weak enough to accept the tissue, but not weak enough for you to die immediately after.

The Essences' hosts are in a similar situation. They must follow through on certain tasks to allow their body to fully accept the burden they now carry. Along the way, they must also figure out how to become powerful enough so that their Essence will be able to find a new host when they die.

The four human hosts must now figure out how to travel to London, England, where they will meet a highly acclaimed professional. This professional had seen death before; although he's not trained in the least, he understands more about the Essences than anybody else ever will.