+Theme as it appears ingame, subject to further tweaks as needed.
According to the oldest and most sacred of Legends of Kasei, Pokemon have existed since man walked the Earth in its humble beginnings. As a matter of fact, the first story told by man says that a certain creature existed before anything else. To truly understand, we must go back many years-when there was nothing else-only the black void of empty space. From the darkness many hands emerged, more numerous than the stars that now dot the sky. From nothing these hands crafted the forces that now make up our universe. Fire. Ice. Lightning. Light. Darkness. The most basic of components grew more and more diverse the longer those hands worked. But then, there was dismay; The Creator could not hope to stop the forces of entropy on his work. Even the most basic elements of all were doomed to fizzle and disappear with enough time.
The Creator realized, while a simple object were at the mercy of entropy and stagnation, a living thing in his image was not. Just as he had created the blank canvas that was universe, he would let other living creatures paint it. From those components he formed the magnificent beasts we know as the True Legendaries. Unfortunately, his creations soon because obsessed their own designs. Unable to compromise on how to detail the new Universe, the creatures fought one and other. The Creator was so dismayed; he retreated to the deepest recesses of creation so he did not have to see his work destroy itself. The war raged on for many millennia, until the very entities of power themselves were exhausted, and unable to fight anymore.
When they looked around however, they saw that their quarrel had created something more. Where the elements clashed, galaxies now existed, and within them, too many planets and stars to count. Unfortunately their battle had left them drained, and they were unable to celebrate their work. The Legendaries faded behind the veil of creation to rest, watched over by their Creator once more.
Fusion and Technology
Team Rocket's roots in Kasei began sixty-five years ago, when Giovanni was in his prime and touring the country's gyms. Watching battle after battle with these mysterious Fusions impressed the man, if these creatures could become this powerful on their own, what if he could control them? Train them to become elite warriors for the Rocket cause? The possibility intrigued him, to the point he returned with his board of executives on his next visit to the region. They all agreed unanimously: Fusions were a ripe berry to be plucked, but the time it took to strengthen the mythic bond between the Pokemon and Humans took far too long to build an army. There had to be a better way; A way to exploit it.
A secret headquarters was erected to the region just north of Kasei: Chugoku. Giovanni himself headed the research team, and Team Rocket's top scientists went to work around the clock studying Kasei's population in secret. Around this time, many Fusions went missing in North Kasei; kidnapped for the research. The project continued steadily for five years, until they finally hit a breakthrough. Rocket scientists built a machine that allowed them to forge an artificial bond between Pokemon and Human, allowing them to fuse immediately.
Quickly they amassed an army by forcing their most powerful Pokemon to fuse with their grunts, and turned their sights on taking Japan by force, starting with Kasei. They had taken all of northern Kasei when the tides started to turn. A hero infiltrated the Rocket Headquarters in Chugoku, and found the mastermind behind the invasion, Giovanni. The result of this battle is unknown to the common man, but Giovanni and the hero disappeared afterwards and haven't been seen since.
Without their leader guide them, the adventuring Teams of Kasei united, and the most powerful trainers in the region poised a final battle against Team Rocket's army. They proved to be too much to the invaders, and Team Rocket was driven back into hiding. The aftermath of the war continues to be felt by Team Rocket, who is now headed by Executive Thorn. A small faction of the Team Rocket continues to believe their true leader will return one day, who are referred to as the Neo Genesis, or the "New Beginning" Rockets.
While modern science cannot explain the origin of humans and Pokemon alike, it is a commonly accepted fact that the two share a special bond with one and other. Legends tell that humans and Pokemon are two sides to the same coin. Just as the True Legendaries and even the Creator had ambitions, emotions, diversity and power, their creations reflect this. Pokemon inherited their types, many forms and phenomenal powers from the raw forces that forged our universe. Humans were born of the emotions, ambitions and will that drove them forward. Because of this relationship, a special bond has always existed between Human and Pokemon.
When Human and Pokemon train together, they develop a spiritual bond with one and other. When this bond becomes strong enough, the two halves can finally unite once more, forming what we know as a Fusion today. It is important to note that despite this mystic bond, extreme physical or emotional trauma can prevent a human or Pokemon from using properly. In such cases, the body of the victim will refuse any new fusions until the subject recovers, if ever. Although rare, it is possible for this to happen to Fusions as well. Fusions who endure extreme trauma may lose their ability to change their form, or fuse with new Pokemon.