Spiritual World

The Spiritual World is an Upper Reality and one of the other major settings that takes place in "Lifestream."

History
The purpose of the Spiritual World was to take in any of the Spirits that come from deceased Livings, and to punish evil Spirits by condemning them to the After World/Alternate Side. As an Upper Reality, the Spiritual World is able to look upon the Living World and observe it while the Living World couldn't do the same. In addition, the Spiritual World also created the "Spiritual Pact" that would involve the Elder Spirits to go and lend an amount of their power over their affinity to a Living. The Great Reality War also took place between the Spiritual World and the After World/Alternate Side.

Lifestream Endowment of a Spirit
It is unknown when exactly does an event take place within the story, but it is assumed that Miki was in the Spiritual World when speaking of past events and her choice to make a pact with Kaika Cho in the Prologue chapter.