There are only two known planes of existence, the Mortal World of Utsushiyo and the Spirit World of Kakuriyo. The Spirit World permeates the Mortal World in every location, with every location on the Mortal World corresponding to a single location in the Spirit World.
The Spirit World is similar to the mundane Mortal World. Where a great mountain stands in the Mortal World, the same mountain stands in the Spirit World
- but in the Spirit World, the mountain is taller and grander, for the Spirit World is home to the great spirit of that mountain. Places on the Mortal World that exhibit some malevolent spiritual influence (graveyards and haunted inns, for example) are sinkholes of negative energy in the Spirit World, the land itself dark and deadly. Conversely, hallowed areas on the Mortal World are green and fair in the Spirit World.
Most of the Spirit World is the domain of lesser spirits that are closely tied to locations on the Mortal World. Most spirits, such as elementals and nature spirits, are bound to a specific location (a mountain, a spring, a single tree) that exists in both the Mortal World and the Spirit World. Other spirits, such as oni and tatsu, wander the Spirit World more freely, either at the behest of more powerful spirits or by their own choice.
Within the Spirit World are the realms of powerful spirits who oversee the operation of the known universe. A traveler through the Spirit World finds great palaces of these spirits, as well as unique heavens and hells. An individual seeking out the Lord of Storms, for example, would find his palace occupying the same general location as storm-wracked peaks on the Mortal World.
A mortal spirit resides fully on the Mortal World as long as the body it inhabits is alive. When a mortal dies, the spirit travels to the Spirit World. It may find its way to a heaven or a hell within the Spirit World, it may reincarnate in the Mortal World in a different body, or sometimes it may linger near its place of death as a ghost.
Different regions of the Spirit World have different names. For example, Jigoku is the place of the dead, while Gakido is the place of ghosts and demons.