The Worlds of the Shadows (translating to "Warudo no Shadou") is a world system of nine different worlds. The worlds that consent of this system are the Samurai World, Detective World, Technology World, Islands World, Scientist World, Bloodlust World, Harvest World, Knight World, and Dark Hollow World.
The World of the Shadows are still currently fighting against the Hollows in the hundred year old conflict known as the Great Hollow-Human War.
Overview
These eight worlds are connected by the Dark Hollow World's reishi lines that the people of those worlds are able to have spiritual awareness to see Hollows and travel among these world by a Spirit Train through Reishi railroad tracks while the Hollows are able to travel through their corrider of darkness, the Garganta and Kumon, and shinobi are able to travel the Worlds of the Shadows through the Sekenta.
The only warrior class worlds that possess only practitioners of chakra to travel into the worlds in need are the Samurai World, Detective World, Islands World, Harvest World, and the Knight World via their affinity for lighting, earth, water, wind, and fire chakra. The Technology World and Scientist World's common intellects and equipments combined were about to design special spiritual power barrier ninjutsus to keep the Hollows outside of their cities and nations as they have conquered five nations per world (expect for the Dark Hollow World which has been conquered at the war's beginning and converted into a Hollow world)
Seventy-five years prior to the main story, Harukugan gathered his Gillian-level soldiers to invaded the Ninja World, starting the Land of Fire.
Events
Formation of the Hollow Axis
Great Hollow-Human War
Big Hollowifying
Worlds
Samurai World
The Samurai World is a world of samurais that fight for honor and respect inhabited by humans. They specialist in kenjutsu and zanjutsu for wielding swords and possess a great affinity for Lightning Style.
They're currently combating the Hollow Axis and are a part with the Human Allies in the Great Hollow-Human War. Most cities are usually in mordern economies, but are under siege by the Hollow Axis and Akatsuki as the Samurai World serves as a Battlefield World (with weaponry being katana, smoke bombs, firework bombs, and etc.) and a Mordern World (with technology enough for vehicles, power, and weapons). Their main militia is the Elite Samurai Force.
Detective World
The Detective World is a world of dectives and law enforcers that enforce law and arrestes criminals (usually thugs, bankrobbers, drugdealers, and international criminals) inhabited by humans. They specialist in gun aiming and gun shooting, dectecive skills, and possess a great affinity for Earth Style.
They're currently protected from the Hollow Axis via versa the World Barrier System and are a part with the Human Allies in the Great Hollow-Human War.
Technology World
The Technology World is a world of people focus solely on technology as they've build not only advanced cities, but micro chips, computers, security robots, systems, and so on inhabited by humans. They specialist in inventing and constructing technology.
They're currently protected from the Hollow Axis via versa the World Barrier System and are a part with the Human Allies in the Great Hollow-Human War.
Scientist World
The Scientist World is a world of scientists and professors with immense amount of knowledge inhabited by humans.
They're currently protected from the Hollow Axis via versa the World Barrier System and are a part with the Human Allies in the Great Hollow-Human War.
Islands World
The Islands World is a world of archipelagos with only four continents full of sailors, navy, and so on inhabited by humans. They specialist in diving, gunning, shipping, fighting skills, technology and possess a great affinity for Water Style.
Bloodlust World
The Bloodlust World
Harvest World
The Harvest World
Knight World
The Knight World
Dark Hollow World
The Dark Hollow World