Spirit Realm

The mythological setting where spirits and Kami reside.
The spirit realm looks much like the mundane one, but time passes differently. When spending a week in the spirit realm, you may find centuries have elapsed back home. Alternately if spending years in the spirit realm, only a week may have gone by for your friends.

Entry

Temples and Shrines often act as the gateway, since once one walks under a torii gate--one crosses over from the mundane to the spiritual.
Take care to only tread on the sides of such paths, because the kami (the gods) walk down the middle.

Examples are in the story of Urashima Taro and Spirited Away.

Illustrated Legends of the Kitano Tenjin Shrine (Kitano Tenjin engi emaki) at the Met Museum

by Amy Winters-Voss