Sokunokuni

Sokunokumi (根の国, "Root Land") is considered the "original realm" from which the kami known as Amatsu-Mikaboshi had held an iron control over all existence. When its hold was broken, by the movements of Yin and Yang, the being had hid itself and the realm itself within the confines of Hell; where it currently resides.

Behind the Scenes
In Japanese mythology, Soku-no-Kumi (根の国, "Root Land/Land of Origin") is the yomi ruled by the god Amatsu-Mikaboshi. It is a realm considered to be the parallel of heaven and reflects the bitterness of the goddess Izanami after she died giving birth to the fire god Kagutsuchi and ended up in the underworld where she eventually became its goddess; trapped behind a boulder that the horrified Izanagi placed there.