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.
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.
Formation of the Hollow Axis
Great Hollow-Human War
The Samurai World is a world of samurais that fight for honor and respect inhabited by humans. They specialize in kenjutsu and zanjutsu for wielding swords and possess a great affinity for Lightning Style.
They're currently combating the Hollow Axis and a part with the Human Allies in the Great Hollow-Human War. Most cities are mordern economies and architectures, but five nations and numbers of cities and town under the control of the Hollow Axis and Akatsuki.
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.
The Detective World is a world of detectives and law enforcers that enforce their laws and arrests criminals (usually thugs, bankrobbers, drugdealers, and international criminals) inhabited by humans. They specialize in guns, aiming, armory, dectecive skills, and possess a great affinity for Earth Style.
They're currently combating the Hollow Axis and a part of the Human Allies in the Great Hollow-Human War. Most cities are mordern
The Technology World is a world of people focusing solely on technology as they've build not only advanced cities, but micro chips, computers, robots, security systems, and so on inhabited by humans. They specialize in inventing and constructing technology.
They're currently combating the Hollow Axis and a part of the Human Allies in the Great Hollow-Human War.
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.
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.
The Bloodlust World
The Harvest World
The Knight World
The Dark Hollow World