Spiritual Realms of Naruto (Illuminate Void)

Within the Naruto World exists six documented Realms where humans and spiritual entities reside.

Overview
Ningen-do ("Realm of Mortals"): Ningen-do is the realm where mortals reside and geographically is where the majority of the humans in the Naruto world live, composed of the Elemental Countries and the lands beyond.

Tengoku ("Heavenly Realm"): Tengoku exists as the realm where the deceased souls of humans pass on.

Jigoku ("Hellish Realm"): Known as purgatory by those enter its realm it is the underworld, where the evil and corrupt souls of humans enter upon their death. Demons and malicious entities are said to call this realm their home.

Yume-do ("Realm of Dreams"): This is the only realm where humans regularly travel to, as they do so everytime they dream. Those in Jigoku have tried to conquer Yume-do but with limited success, having only crafting demons capable of creating nightmares or appearing before humans to goad them into evil. This realm is important as it is composed of dreams and imagination, an ever changing world that allows humans to revitalize their mental and spiritual strength.

Saichuu-do ("Middle Realm"): This realm is an intermediary world, that overlaps the others, faciliating travel between each of the realms. It is through this world that ghosts, and evil spirits exist on the Human Realm due to how weak its barriers are. Spiritual creatures are able to nagivate through this world, which appears as a grayed version of our world, although it is slow to adjust to the ever changing aspects of the human world. Therefore where one might find a village in the human world, they would instead find lush forest or even a mountain in its place.

Chikushu-do ("Realm of Animals"): Animals do not reside in neither heaven nor hell instead they are reborn in Chikushu-d0, which also serves as the home for all of the Summons. Through contracts humans are able to summon creatures from varying clans to serve as companions in Ningen-do.

Trivia

 * The concepts of the various realms has obvious references to Buddhism, and the Rokugan Setting.