The mutual possession of the ten realms (Jikkai-gogu) means that each of the ten realms of living existence contains the characteristics of the other nine realms. The realm of hell to the realm of heavenly beings are known as the “Six Regions” which are the realms of transmigration (rebirth) one reaches according to karma, or the deeds of one’s previous lives. The realm of Srāvaka to the realm of Buddhahood are the realms of “the four holy ones” or those who transcend the cycle of transmigration.

“Spiritual contemplation (kanjin) means for one to meditate on his own mind, observing through it ten realms, from the hells up to the realm of Buddhas, all of which are by nature contained in every mind.” (Kanjin Honzon Shō, WNS2, p. 131).