In modern Japanese parlance, kaijin literally means "strange being".

Supposedly, the term originated from the 1936 Japanese mystery novel, "The Fiend of Twenty Faces", where it was used to describe the master detective's nemesis, the eponymous "Fiend" who was a master of disguise. It wouldn't be until 1971 when the series "Kamen Rider" debuted, and the first true kaijin graced the screens of televisions all across Japan.

In that very first series, the kaijin were genetically and cybernetically modified humans created by an evil organization known as "Shocker" as a means to take over the world and destroy the eponymous hero, Kamen Rider. Ever since then however, kaijin became a universal term to refer to the various types of monstrous humanoids used in both future iterations of Kamen Rider and it's sibling shows, Super Sentai and Ultraman.

Each series had a different name for the kaijins that severed as the antagonist for that year, with some sharing similar motifs to the ones that came before them, but they were always unique and distinct enough to have viewers know what type of kaijin an individual one belonged to.

Some kaijin were mutated humans, intentionally made or not, others were cyborgs, the spirits of the dead, alien invaders, or the pure embodiment of the human unconsciousness. Regardless of their origins, kaijin have become an indispensable part of Kamen Rider and shows like it.

At least...that's what they are on Earth. On Valresta, the term kaijin have a very...different meaning, for that's due to them being associated with certain individuals throughout history.

The Drunkard of the Dead.

The Invulnerable Storm Queen.

The Demon Painter of Dreams.

The Clockwork Overlord

These were the names of (in)famous and powerful warriors throughout the history of Valresta, but their strength was only half of the reason for their infamy.

The Drunkard was known to linger around ancient battlefields and create armies of the dead with the sheer force of his shouts.

The Storm Queen was always accompanied by a fellowship of fierce knights, born from tide and fury, that made sea monsters look like guppies in comparison.

The Demon Painter could stare into the eyes of his enemies and make the perfect counter, making monsters that were blend of their phobias and weaknesses.

The Clock Overlord spent his days in workshop under a mountain, surrounded by handmade aether puppets that had more personality and soul than most humans.

Despite how discordant their titles were, all of these warriors shared the ability to create life from nothing, to lead armies of warriors that had grunts who were fiercer and stronger than even the most dangerous overlords. That even if one were to ambush them ten to one, they could wave their hands and make a squad of fighters where each individual member could easily fight off one hundred to one.

But it takes years, sometimes even lifetimes, for the most talented of cultivators to reach such heights. It should be impossible for someone to be able to create monstrous warriors in the blink of an eye, that could topple hegemonies right from the moment of their conception...right?

Such a power only belongs to those of a divine nature...shouldn't it?

In the world of Valresta, kaijin are nothing more than rumor and legend. But whether or not that's by design or by the natural movement of time, no one knows for sure.

But...there is one thing that can be certain.

If the kaijin ever become confirmed to be real, and the source of how to make them ever becomes known, then the world would plunge into utter madness in pursuit of this power.

So let's hope whoever ends up inheriting this secret, knows whatever the hell they're doing...

Author's note:

The chapters in the Auxiliary volume are exactly that, auxiliary.

They're designed to provide world building context that could not fit in the main story.

Feel free to read them or skip through at your leisure.

Thank you.